/usr/bin had a SHITLOAD of stuff that came with my default install.
/bin had the limited amount of stuff needed when booted single user for maintainance, but certainly not 90% of the system supplied text processing apps, or the compilers, or the nroff/troff stuff, or the (you get the point) (I hope).
My stuff was late 70s early 80s gear. I was paying close attention to the Sys V/BSD differences since I had to port my code between them, and the bastardized Xenix systems.