I think you're reading or portraying that wrong. Pop!_OS and Nobara are about 9% behind in frametime, i.e. their frametimes are 9% lower. That's a good thing!
The charts don't make this particularly clear, but the text summary mentions "Windows is stronger in terms of 1% percentile frame times.".
It's still open to interpretation what exactly they are measuring with their frame timings, e.g. is Windows consistently generating frames within 10.6ms but Nobora is up to 9% less performant then that, sometimes 11.6ms? Although this only seems to be for the 1% lows. I don't think it's a particularly insightful metric in this particular benchmark.
