This was surprisingly interesting! Thanks for posting it. I didn't think there was anything noteworthy to glean from it, but @[email protected] mentioned down below that USB doesn't have interrupts, which I was unaware of. I especially liked how he covered different types of USB keyboards running at different speeds, and he briefly covered n-key rollover, or the lack thereof on the two keyboards he had on hand as well as why some key combinations fail due to shared wiring in the keyboard. The latency discussion between PS/2 interrupting and USB being polled for data at the end of the video was also fascinating.

Edit: Ben Eater did a follow-up video on how n-key rollover works: https://www.youtube.com/watch?v=2lPzTU-3ONI