Here is an idea. Run your own experiment. Create a Strava segment on a longish downhill that will take at least a couple minutes to roll down without pedaling. Next start at low pressure and run down the segment a few times. Add pressure and repeat. Any RR difference will show up as an average time difference.
The reason I think that this is a divisive topic is that inflation pressure isn’t that important for speed. It’s down in the noise and difficult to measure a true diffence. Otherwise, if there was a large difference there would be universal consensus on what pressure to run.
Then run the pressure that feels the best to you and you don’t get pinch flats or blow the tire off the rim. There is no wrong pressure. (There, I said it)