These fake-time environments let you set the time, so you can test how the code will behave in 2039 without waiting for 13 years. For Go's synctest, 1-1-2000 is just the default initial value for now().
But still a kludge. Better: use something equivalent to Go's testing/synctest[0] package, which lets you write tests that run in a bubble where time is fixed and deterministic.
The reason is simple: they'd like to reap all the benefits of a permissive licence (many people and companies won't or can't touch GPL code), without any of the downsides; but these downsides are the very reason behind the rules in more 'restrictive' licenses like the GPL.
This usually doesn't work, and in the end all they can do is complain about behaviours that their license choice explicitly allowed.
Go did exactly that, where Maven's 'Project group identifier' is an URL you control, e.g. github.com/<your-account> but also <your-website>/go-pkg or whatever you want. Other languages did this too. Flat namespaces are more of a Rust issue (among newer languages).
The real issue here is Rust's flat namespace. In Go, for example, there's no ffmpeg crate, there's github.com/someone/ffmpeg and gitlab.com/someone-else/ffmpeg, and so on. There's no blessed, unique 'ffmpeg' package, you can't squat names, and if the first package gets abandoned, you can fork it under a new path while keeping the 'ffmpeg' name. Only the import path changes.