It's sort of hard to say but I'll give you an example. You can only use the Stealin' card right after a gate card has been set. You can't use it whenever you want because technically a gate card has been set already.
The biggest and most annoying loophole ever in other words.
I'm sure Kiohl wants to be able to use all his Ability Cards, to have a better strategy, but the Bakugan doesn't have to open. In the rules it says that, if the Bakugan stays on the gatecard(magnet down or not) it counts.