“There was no doubt that the narrowest tires were slower than slightly wider ones.”
Cyclists rode skinny tires at rock-hard pressures for a century because everyone knew they were faster. Nobody had tested it on real roads with a real rider. Once someone did, the pro teams checked the results and moved from 23 to 25 mm. The buried detail is that the tester sells wide tires, so the next test should come from somebody else.