Definitely a subfield thing in part. Highly theoretical CS PhDs (complexity theory, algorithms, etc - the folks who are mathematicians in computer scientist's clothing) almost always require postdocs, both because they tend to be less heavily recruited by industry, and because the vast majority of departments are shying away from theory in favor of things that bring in more grant money and industry partnerships.
Departments aren't stupid, though. They realize that grabbing star grad students with highly marketable skills in industry as they are walking out of their dissertation defense is probably the only shot they'll have at getting them. They will often "try out" industry or take a job at Google or MSR on the advice of their PI, noting that it's just as good as a postdoc but pays four or five times as much. Problem is, they then have to walk away from their $180k/year to take a faculty position that might not pay half that and could very well dead-end in a few years if the department leadership changes (or any of a dozen other precipitating factors) and they don't get tenure.
All that said, I personally know of tenure-track professors at two of the schools you mentioned, plus ones at quite a few other top-flight CS departments (Cornell, Toronto, Washington, Cal), who were hired straight out of grad school.
I've had dozens of Chinese students in my classes and graduate rotations. I'm in a technical field and it's a competitive program, and I don't think I've ever encountered a student who couldn't cut it in terms of doing the rigorous work required. On the whole, my Chinese students have been as good or better than their local peers, which is true of most foreign national students: kids who have busted their asses to navigate the difficult academic, bureaucratic, and cultural hurdles to succeeding in an overseas university are typically self-selecting for aptitude and a good work ethic.
That said, I've also found a massively higher level of barefaced cheating, including things like copying and pasting code that previous students had inadvisably put on github, and that after I specifically said I'm aware of the existence of that code and will check for it. Or homework answers that are perfectly correct - if you were answering the homework given to a previous quarter's version of the class, rather than the current version with changes to the specifics. Or looking up answers on smartphones in the middle of a test, and then attempting to ignore the fact that they had been caught.
And it isn't just the cheating: it's the indignation when confronted about it. It's almost never denial, but rather something along the lines of "I did this because I have a lot of work to do. Just don't worry about it this time, I won't cheat on the next one."
It's especially upsetting because the kids aren't incapable of doing the work, they just seem to think that's it's totally acceptable to cheat their way through classes when they feel like it. While it's no more noble or allowable for kids who are in over their heads and unable to do the work cheat, it's at least somewhat understandable. Cheating out of some combination of arrogance and indifference is far more alien to me.
There's a second major problem very specific to Chinese students, that I assume is related to the first: shocking lack of English language skills. I say shocking because these are students who have theoretically scored very high on the SAT or GRE. While I'm in a technical field, we still insist on at least decent verbal scores plus high TOEFL scores for admissions, and yet I regularly get students who have major trouble parsing even very simple written English instructions. I've never noticed the same issue with students from other Asian countries, so I have always wondered if there's some "system" for Chinese students, consisting of either outright cheating on the standardized tests or else some rote memorization techniques that result in acceptable test scores but little-to-no actual English learning.
I'm not a crazy outlier in my department, most faculty who aren't either in or hope to be in leadership positions that require lots of under-the-table footsies with the administration have voiced similar concerns. The administration can't get enough of those inflated foreign tuitions, though, so they aren't likely to do anything substantive on the issue. They've tried to do outreach to get the point across that cheating, both before and after entry to the university, is not acceptable behavior, but from everything I've seen it's water off a duck's back.
Finally, I'm not some closet racist who wants to bring back the lily white college campuses of the bad old days. As I noted, foreign students are, on a whole, much more studios and less likely to take their education for granted when compared to domestic students. And "on a whole" in this case includes Chinese students! The problem isn't that Chinese students (or students of any nationality) are inherently bad: it's that we are sorely lacking in tools to adequately evaluate them for admissions and to get them to understand and respect academic integrity rules.
Departments aren't stupid, though. They realize that grabbing star grad students with highly marketable skills in industry as they are walking out of their dissertation defense is probably the only shot they'll have at getting them. They will often "try out" industry or take a job at Google or MSR on the advice of their PI, noting that it's just as good as a postdoc but pays four or five times as much. Problem is, they then have to walk away from their $180k/year to take a faculty position that might not pay half that and could very well dead-end in a few years if the department leadership changes (or any of a dozen other precipitating factors) and they don't get tenure.
All that said, I personally know of tenure-track professors at two of the schools you mentioned, plus ones at quite a few other top-flight CS departments (Cornell, Toronto, Washington, Cal), who were hired straight out of grad school.