Sort of, they’ve effectively abandoned the trash can Mac Pro and are working on a whole new design: https://daringfireball.net/2017/04/the_mac_pro_lives

That’s the only real instance I can think of though!

There was an iPod Shuffle model with buttons only on the headphone cable, and voice control. I believe the subsequent models were more conventional.

They removed the dual drive option on the Mac mini. The Mac Pro redesign has also been mentioned. I'm sure there are other (less notable) instances of backtracking that aren't occurring to me at the moment.

The G4 Cube...

They're currently working on a Mac Pro backtrack; moving from this super-powerful tube to something modular like previous Pros

I wouldn't dare call such a thermally-compromised[1] computer "super-powerful"

1. http://www.anandtech.com/show/11245/apple-to-redesign-mac-pr...