The very first rules(B1 series) didn't even have Ability Cards to play with so there were no rules for it. I'm with the play as many as you want, meaning you can play all 3 of your abilities if you wanted in one battle if you wanted. Seems to me people just base the 1 Ability card per battle off the first show.
Actually, B1s did ahve abilities. Series 2 started with abilities though you are partially correct as the very start of Bakugan, Series 1, did not have abilities. But yes you can play all if you really wanted to. The rules state dierectly that when playing ability cards (I think the player whose turn it is goes first) each player goes back and forth and you only stop when both players pass on playing one.