As long as they keep track of high scores separately for each character, I don't have a problem with the stages not being character-specific. Then again, the language was vague enough that I don't think it's confirmed one way or another. It's also possible that there are only five maps, but the targets are placed differently for each character - we just don't know.
I do agree with EasyCure that the Target stages have always been about mastering each character's moveset... but I do think that, even with non-character-specific stages, they can still make it so. What's a piece of cake for most characters may still be a devious puzzle for others, and they'll probably balance that out so that each character must make clever use of all its moves. Still, that's why I'm hoping for individual high scores for each character, because any given stage will be easier for some than for others, and I'd hate for there to be a "right" character for each stage.