Yes I oversimplified. Large supple low pressure gets faster the rougher the surface is. If the road is glass-smooth, then probably the skinniest hardest possible tire wins. I expect there is a best solution for each pavement type, airspeed, rider weight and probably some more factors. Especially if your defnition of "speed" includes human fators like fatigue and recovery — speed the NEXT day is very important to a stage racer, or to a weekend warrior. That's is a complicated landscape to navigate exactly, by theory or empirically, so we muddle along and feel our way to the best solution for each of our situations.

The pros are mostly more scientific about it these days, but in the past (talking decades back) they were often held back by hidebound stubborn old hands who replied on lore they picked up when they were young, from other unscientific types. The occasional show of testing with instrumentation was usually at least in part a marketing effort, and it always just confirmed what they were already doing was right. Hapyy to hear of counter-examples, I'm sure there must be some where the testing actually taught them something.

I don't know how much science went into the pros deciding more recently to use wider tires and how much is the bike industry needing some way to make last years models obsolete. The fact that their move to wider tires seems to validate what I and others were saying, long before the pros got on board, could just be luck or random variation for product differentitation. I'm well aware that my wish that it be true causes confirmation bias, so I'm not going to claim any kind of proof. But it's my gut feeling, that on most real roads, wider tires prevent fatigue that makes you slower later in the ride and tomorrow, and that is speed. Plus even a small reduction in the jostling of your guts, muscles and connective tissue, which are lossy, could theoretically make you actually faster, even without the fatigue reduction and recovery factors.

But none of this is proved, fer sure.