Pakl said:
Set multipliers mever changed in Z... What makes you think Gotenks is an exception?
Ahill already covered the bulk of why. To add to that, there's the simple fact that Toriyama didn't write the plot with numbers in mind. To have battle power numbers and multipliers dictate the plot it the flawed notion of a fan perspective. The battle powers at the start of Z and how they correlate with statements and feats from Part 1 are enough to prove such.
Characters' strength should be judged by the feats and statements surrounding them, not rigid multipliers even the series' creator found to be irrelevant.
I choose to say it was gag... The entire scan was gag anyway.... Gotenks is a gag character... What makes you think he is SSjin 2 tier? Piccolo said he was strong but still weak for Boo..m he can be in par with Perfect Cell for all we know...
Then you're clearly confusing a gag character with a comedic one. The former tend to have inconsistent feats or exist purely for the sake of comedy. For example, Mr. Satan can be considered a gag character during the Cell Games due to surviving far more physical punishment than he should be capable of and overall existing purely for comedy. Arale is a gag character because she can evidently be as strong as the plot demands and characters even call her out as such.
Gotenks on the other hand is a comedic character. Whilst acting overly comedic, his role in the plot is taken seriously by the characters, as is his strength by Boo. If he were a gag character, then him being absorbed by Boo and the fight against Gohan that followed would be treat as such, yet that clearly wasn't the case.
Base Vegetto is a different story.. Potara is much stronger than fusion... Goku and Vegeta are much stronger than the kids and their fusion os more competent due to rival boost...
If there's a major exception to this rule of yours, it calls the very existence of this rule into question.