You're missing the point.
You mentioned base Goku vs. 4th form Freeza like it matters here... Thing is, base Goku took his fight with Freeza VERY seriously, but didn't take his sparring match with Fit Boo seriously at all... As a quick/easy example: base Goku actually powered up against Freeza, but NEVER powered up against Boo.
IOW, it's faulty to use the base Goku/Freeza showing as any kind of measuring stick where Fit Boo is concerned. All we know is that Fit Boo was a little stronger than Fat Boo, but that's hardly enough to put him on par with Boohan.