As far as I know the .net debugger infrastructure is not open source, so unless you are happy to stay within the confines of VSCode, I think that your options are pretty limited for stepping through your code.
It really depends on the workflow and scale of operation the cutting tool manufacturer. Some focus mostly on small batches of very specialized tools, and some focus on producing huge volumes of standardized cutting tools. And anything in between of course.
Whatever the grinding machine that is used, there is always a necessary setup step before the production run. The setup involves installing some equipment on the cnc machine, heating up to operation temperature, calibration, dry run to check for possible collisions and grinding a few pieces and check that they are within specs.
The name of the game is then, given typical customer order or target market, to find the right balance between the utilisation of the different machines, human intervention and automation while optimizing for cost and cutting tool quality.
In the video, it look like it is a pretty small manufacturer doing small specialized batches. In this case most of the time is spent doing machine setup and quality control, and the drill value doesn't justify the investment into a more complex or automated system.
The "four to five" hours they mention is probably the time required to setup the grinding center, maybe dress the wheels, do some fine adjustments on the grinding process. Once the machine is setup, grinding each drill is just a few minutes.
The grinding machines they are using seems to require quite a bit of manual handling, but cnc grinding center where everything is automated also exists.
Actually, the grinding of the flutes is shown very briefly around 3:35. Filming this operation on such a small scale is difficult because of the geometry of the system and the grinding process: the drill blank is supported from below to prevent the carbide from snapping under the load, and the wheel grinds from above. The grinding wheel is order of magnitudes larger in diameter than the diameter of the drill it is grinding. Also, everything is flooded with cutting fluid.
There are hundred of videos showing the process on youtube if you look for "cnc grinding drill".
I've been using Omnisharp for ages, but I could never get netcoredbg working.
Last time I tried te integration with emacs-dap it kept segfaulting for no obvious reason.
But I may give it another try now!