You are leaning way too hard on point estimates of R0. The way people estimate R0 is noisy, and the error bars on these estimates are significant. It's fairly pointless to take any two papers and compare the values as if they're precise.
This literature review has estimates of R0 for flu running from 1.06-3.4, and rhinovirus running from 1.2-1.83:
In the particular conditions we created in 2020, the Rhinovirus was better able to spread than the Flu. Why?
Because people were on the lookout for fever (and other things like continuous cough etc). Flu causes fever, and anyone who got a fever and was sensibly-minded would self isolate at least for a few days until they got test results or until symptoms abated. Whereas Rhinovirus is much less likely to cause a fever, so people twig that they've 'just got a cold' and carry on going about their day.
Especially for schoolkids - if they've got a fever, they're kept at home. If they've just got a snotty nose then they're likely to still go to school.
So Rhiniovirus was able to fly under the radar whereas Flu wasn't.
Could be. Covid is certainly more flu-like than rhinovirus-like. Kids were also not in school, and kids are historically a big spreader of influenza.
I generally think people look for "fancy" explanations for the trends, when simpler explanations (i.e. people weren't going to the doctor) work just as well.
This literature review has estimates of R0 for flu running from 1.06-3.4, and rhinovirus running from 1.2-1.83:
https://www.medrxiv.org/content/10.1101/2020.02.04.20020404v...
Given the uncertainties involved, these ranges are effectively identical, with flu maybe being a bit more contagious.