For tender cuts of meat (like a good steak) it might be true that temperature is what matters. But cooking sous vide for 12-24 hours can turn a tough cut into incredibly tender juicy meat - the connective tissue needs time as well as temperature to break down.

It's quadratic. You need four times longer for a steak that's twice as thick.

I've certainly overcooked more than a few steaks due to cooking too long, not too hot. Also, it seems it sometimes depends on meat quality (not just the cut). Or maybe it was the sear that I tend to overdo.