It was actually pretty great when I worked for a company making things here in england:
“That needs to move 50cm” meant it had to move exactly 500mm
“That needs to move a foot” meant just kick it over about a foot

It was just an unspoken thing that metric meant precise and imperial was just caveman measuring

I think most of the horror stories are from people printing way too fast and too low
Many people print with too small z-offset because “that’s when it sticks”. you can get away with it in pla but petg will just become a mess

It’s not stateless end-to-end, it just means the client needs to keep track and pass the state rather than drivers or hardware

I’m not 100% on the motivation but from an architectural standpoint it does make sense - your software can now do many new and weird things without a hardware change

One example I saw was allowing an arbitrary number of streams to be processed simultaneously, just passing the different context state for each stream