I put in a lot of miles on slotted cleats in the early 80's, before I switched to clipless pedals in 85.
Yes, they were a bit nerve wracking when the slotted cleats were brand new, as the slot tends to be tight on the pedal cage. But after a rew miles of use, they always wear in a bit, enough that it gets easier to get your shoe off the pedal after a quick flick of the strap buckle. After only a season riding slotted cleats with toe clips and straps, gettin in and out of them pretty much became muscle memory to me. The slot also, eventually wears down at the corners enough that you might get a degree or so of lateral play that makes them a bit more comfortable on the knees.
What I remember was, there were lots of bolt patterns for cleats, mostly proprietary to the brand shoe the came in.
​​​​They came in either one, two or three bolt patterns with different spacings and locations.
I don't think there was a "standard" bolt pattern that was used by most cycling shoe manufacturers like we now have with the Look cleatless pedals.