yes that is a classic report thor and invisiblehand, and quite good, even if data jumps a little more than appreciated. if i remember correctly 11 not-worn cog and 175 watts had something like 88 percent efficiency. ouch. higher cadency than 60 was also unbeneficial, especially with smaller cogs
figures cited elsewhere from for example frictionfacts has consistent data to a degree where you might suspect they are interpolated. but it shows the same thing; resistance jumps when you go from 13 to 12 to 11 even if the watt figures in their system are very low. have also been skeptical to their report that a smaller chainwheel should give higher resistance. it is very obvious if you have tried really large chainwheels that things are the other way around. as chain speed increases, so does resistance caused by the jockey wheels, it gets bad for chainwheels over 90t. 61 and 69 is without any noticeable drag in my subjective experience, 87 is just a bit draggy, havent tried inbetween the latter.
results from load of 300-500 watts are common, these are always better, and necessary to reach commonly cited dream figures of 98 percent.
but my suspiscion over the 11 came from own experience when i made a hybrid gear system with half-gears many years ago by welding cogs to a torpedo 3-gear hub. it was then very easy to asses with your own legs the difference between having a certain gear ratio over direct drive and 11, vs planetary drive and 15 resulting in the very same gearing. what a difference in efficiency.
the same experiment is easy to make for anyone on a road bike with front derailleur. just calculate what cog to use with the large chainwheel engaged, and compare to the small chainwheel on 11. (btw chainline have in studies from ihpa been shown to have smaller than expected importance) if you dont have a completely new and fresh drivetrain you will likely never want to use that 11 again? it could in some cases feel as bad as cranking the bike with an oldfashioned friction drive generator. also try spinning the cranks with your hands, its may be easier to get the feel of resistance that way.