JayKay3000

Anecdotally remembering studies and opinion is because a 23c tire will be faster on a smooth surface, but most roads are not smooth. As you ride the bumps in the road push against the hard tire and slow you down. A cattle grid with the spaced metal slats shows off this quite well too. A lower PSI tire is able to absorb these small bumps and roll over them rather than being deflected by them. You can try this yourself when you find a patched bit of road that super smooth compared to an older bit of road that's slightly worn and then add in some that's starting to crack up and your momentum is sapped and you have to work a lot harder for the speed.

However, you need to be careful that you don't air your tires too low else you'll get snakebites where the rim and the inner tube are squished together causing a tear, thus a puncture.

The poor surface can slow you down by making you less efficient riding and thus slower. It's hard to pedal efficiently when the bicycle is juddering and bouncing all over the place.

However, tire width is different from how well the tire rolls. You still need to have a slick or fast rolling compound if you want your bigger tire to be anywhere near as good as a thin tire.

Remember that there is also a bigger contact patch on the surface of the road which should give you a bit more grip. It's a bit like how disk brakes weigh heavier, but for the average rider they'll have more confidence to brake later in adverse conditions so will end up being faster. Disk brakes just work better in the wet - not massively better some would argue, but enough to give a rider a lot more confidence.

I run my 23C tires at 80PSI. (I've had my rear go down as low as 60psi without any issue (also without noticing!) But then if I weigh up the bike a lot I might put more air in them.