First gen intel MacBook - Core Duo 32bit, year that later they used Core
2Duo 64bit and double ram capacity
First gen Apple Watches - not waterproof.
First gen iPad - no camera that actually faces you.
First gen iPhone - only 2g, no front facing camera.
First gen Unibody MacBook Pro - Exactly the same as previous gen MacBook unibody, errr without a replaceable battery.
First gen iPod - Firewire rather than USB
First gen Macbook 12" ... slow as hell, keyboard issues
I'm sure your M1 won't fall into the above category, but you see there has been a trend from time to time