Yeah, but that doesn't change anything.
Rock beating Bass is a given. I mean Rock, Duo and Sunstar are like the top-tiers of the Classic Era with Proto and Bass being just nearby. With statements like Proto admitting Rock may be the 'superior model' and Bass not being able to ever defeat Mega Man due to him having something to fight for, it's easy to see. So yeah Rock > Bass and probably Proto by default. Also sure, Bass lost to Rock in MM8 despite his Treble Boost and Evil Energy but that also could've been caused by Evil Energy making him unstable and making him overconfident in his new power with it (in addition to Mega being superior). Regardless of Bass losing though, the fact that he fights on par with a serious, and sometimes pissed off, Mega Man is more concrete and telling than Proto's held back fights against him as it's harder to gauge how powerful Proto really is as a result.
Meanwhile, King managed to chop down Proto with a single swing before he could react and Bass defeats King just fine by keeping up with him and tanking his attacks. That's in addition to fighting on par with Rock on several occasions. That already shows how powerful Bass is compared to Proto.