My take on it is a bit different…
The entry speed was almost certainly different between tires because they started from a stop uphill of the beginning of the speed trap. I’m thinking you’d coast up to speed faster with faster tires. We probably should argue that this magnifies the difference between tires but faster tires will roll up faster so they hit the speed trap going faster than slower tires.
I think wristwatches are plenty accurate to .5 seconds and if you’ve got two guys testing and the results show the same thing then that’s not too bad. A light beam and electronic timing would be more accurate but my opinion is that this is accurate enough to see the difference.
The latex tubes getting hole from rubbing… Maybe they were talking about after you’ve ridden them for awhile (months). I’d bet they can change out an innertube with skill, they’ve been at it (riding that is…) for awhile. I’d be really surprised if they had the tubes pinched but we don’t know for sure I guess.
And finally hard rubber…does it run slower on a steel drum? They said hard rubber is slower on the road.
I didn’t see where they had the individual runs for the different tubes published…but they did say that within .5s should be considered equal in performance. The difference in times were .6s for the mitsuboshi 650X37mm and .4s for the deda giro d’italia 700X24.5mm so it’s not a big difference. They used michelin latex tubes which they said where thicker than other brands so that might matter too. Then they ran thin butyl tubes vs. thick butyl tubes and found no difference. On still another hand Frank Berto in his e-book “all about tire inflation” feels proper inflation is a big deal, in the bike quarterly article they didn’t find a big difference at varying pressures.
I thought I could really tell the difference riding my mtb in the 90’s with latex, ultimately I switched back because of rubbing “puncture” problems, now I’m on tubeless but they sure felt good.