I'd say it could be good AND bad, you could lose Pikmin but they would always be there spinning, in a way it's like a Pikmin bank, store Pikmin there until you need them or until the opponent gets latched, you can easily go and break the block to recover your Pikmin. Of course if you were to fall one Pikmin short a recovery, you'd be pretty bummed you let the little guy spin. But making two spin is a fun trap for play with friends lol. Especially if they are the same color and so your opponent thinks there is only one but ends up with the double the damage they expected.
It really depends on how well you use this little glitch =\
And I guess you could use it to single out your Yellow and Purple Pikmin...for whatever reason you would want to do that, maybe some aerials or a humorous Up Throw KO...I dunno
BTW doing it with three Olimars makes the game freeze