Clearly you haven't played other games besides Kingdom Hearts 2.
I've played and maxed out all games but Birth by Sleep and Dream Drop Distance. I'm not going to spend so much money on a console I will barely play.
I'd say that it's just how I play all my games. I never have to grind to beat the next boss because I take the time to explore
everything over, like checking if a character would have a different line to say and constantly being ambushed by enemies. It's obsessive for 100% completionists so I guess I wasn't completely farming intentionally. The most difficult time I had in KH was with 358/2 days on proud mode. Where there weren't enough enemies to smash.
KH1 had some pretty hard bosses, and the final boss was challenging as well except for his FINAL form, which was a joke.)
I gotta admit, that bastard and his 7 or so huge-ass forms did take me a few tries, but that was overcame without any grinding (I don't think you could on the island anyway)
Riku in his dark form was probably the hardest for me in the first game, You just had to keep dodging and clashing with him.
Welp. I used to know everything about the entire series before the latest games. Forgot most of it now... I keep saying to myself that I will set up the PS2 again.