That reason is not functional. Every stat of every comic character like Thor isn't saying they're at the "exact same level against everyone", it depends on context the the stat portrays what's most consistent. Thor had that stat against a Hulk on that level, Loki, Wrecker, the Thing, Dr. Doom, Namor, Super Skrull and the High Evolutionary (and Magneto, I'm pretty sure), there is literally no way this isn't something that shouldn't be reflected in his profile. Not to mention that those characters have their own feats and scaling that Thor is a "small" part of for their 5-B stat to be consistent, and we need to see progressively if 5-B is truely consistent or something lower or higher should replace it based on all the information about it we have.
The explanations for his stats could simply say pretty much "However, Thor doesn't obligatorily always hold back at the exact same level, and can reach higher or
lower levels if he wants to without reaching his standard stats"
Also one of the scans that state that he holds back say that when he does so he uses "a third of his power", and while it's not a literal a third if we do math exactly, that can very much be taken in as him using the exact same level against everyone, even if you ignore all the scaling.