The logic was just that when UNIX was originally evolving, they ran out of disk space on their PDP-11 and had to start moving less-essential binaries to a different disk. That’s why it’s “/usr/” which was originally for user data but that disk happened to have free space.
Any other explanation is just retcon. Some distros try to simplify things.
White guy in Japan. A lot of people will assume I don’t speak any Japanese (=am a tourist). I’ve had it many times where after a transaction at a shop, the staff literally tells me “I’m so glad you spoke Japanese, I was so afraid when you walked up since I can’t speak English”