that baten kaitos is a very weird game is something i can't imagine being lost on anyone who makes it past the first few hours, but i played it before i was familiar with other rpgs or playstation 1/2 games in general and it was only much later i realized it (along with the sequel) was maybe the only game of that generation i know of to use the square pre-rendered background style heavily and that was why the game looks...like that
it almost seems weird to call using techniques that had come to be seen as outdated by the time they were releasing (and surely even while they were working on) the game a "flex" but i feel like there's no other way to describe some of what's going on here. i think other games like radiata stories, valkyrie profile 2, and devil may cry 1-4 also make great use of the strengths of taking camera control away from players and highlight a lot of what appeals about it to me, but those still use fully real-time environments...there's nothing else i've ever seen that looks like this. the artists have taken some of the ideas late-ps1-era square were playing with like legend of mana's occasional fmv-captured animated background elements and use them to do things like create constantly billowing clouds and flowing rivers, on top of just using sheer detail to really give each area a different character from the others. that's before you get into some of the really weird ones like reverence where the flat design is probably genuinely the most logical way to convey them to the player.
there is an area i think might actually be fully modeled but i actually can't tell because there's a whole other kind of camera trickery going on there such that i really can't make out what's going on behind it. but the thing i got to tonight that genuinely blew my mind seeing it for the first time in forever was the snow cliffs, where above the background layer is...some kind of crudely modeled snow system where you (and some of the monster icons) leave huge trails in it temporarily as you move through it, and also the foreground layer has this wind that affects how fast you move in a given direction. literally who gave them enough money to do all this stuff
i can't remember if the sequel actually mostly repurposes a lot of backgrounds or not, but i do have the reminiscence that (especially thinking about stuff like there only being 3 playable characters) it's got a bit of a "we did not have the same budget" feeling