That makes a lot of sense. I'd actually always wondered how the Animorphs could consistently beat Hork-bajir in combat. If you showed me a Hork-bajir, and asked me who would win in a fight between that and a tiger/bear/gorilla/wolf, I would put all my money on the Hork-bajir, every time. I generally tended to think it was because the Hork-bajir had been herbivores with no natural predators, and thus would have no natural instinct for fighting; the Yeerks that controlled them therefore wouldn't have the benefit of that instinctual knowledge, either.
Either way, though, Hork-bajir still makes sense as a battle morph.
Because hork-bajir controllers were never trained to fight Earth's wildlife. Let alone those working as a team, fitted with human brains.
When you think about it, hork-bajirs were used most of the time as guards at Yeerk Pools, or other specific spots. Because in every other occassion they had human controllers to use.
Even if h-b controllers met wildlife, they would always just blast it off from safe distance, if necessary.
Now on the other hand, as I said Animorphs were dedicated, they had advantage of beforeseeing, planning in advance and so on. Combine that with teamwork between all of them, reconnaissance information and element of surprise, and you will have pretty good odds.
Also it was hard for hork-bajir controllers to adapt to the strategies of Animorphs, because most of the time those who survived encounters would probably have been executed by V3. And those who didn't, well chances are pretty slim that they would meet them again, and even then Animorphs did swap between battle morphs every now and then.