As with many TB discussions, we haven't defined our terms and so we can both be correct. I'll confirm with you that I can play basses with different mensures with a 30 minute practice with better than average intonation, but... IMO, I cannot play those other basses nearly as well as my 3/4. Victor Wooten, John Patitucci, Christian McBride, and Marcus Miller have nothing to fear when I pick up a fretless bass guitar because about ALL I get right is time and intonation, and there's several more dimensions to that instrument that I don't even begin to touch. To Damon's point, they ARE different.
Different mensure instruments for practice - completely down with that. Different mensure instruments for the occasional well-prepped tune, okay. More than one mensure for "totally bringing it like Rufus"... not even.