Rockstar doesn’t exactly create multiplayer maps os scenes in deep need of gameplay balance.
I mean, you run and shoot at people.
I can see them only testing and using BSPs or blocks to beta test missions only.
But as soon as you’re trying to design something focused on a specific gameplay flow and you want to fine tune stuff you have to say goodbye to such a flow.
You can’t really start a platformer with exact sprites and or 3d models. What if you want your character to acquire an exact speed to jump over that fire? Imagine making a Mario 64 level starting with a 3d models. Could you make a multiplayer level directly with 3d models? What if you start testing the gameplay, the level flow and you notice that building X, room Y is unbalanced and offers wrong line of sights, no cover for team A or you want to add some (let’s add another floor so to increase verticality in specific section of the map).
Serious level design is about trying and trying, applying ideas fast and being ready to change them constantly and even throw them away if they don’t work.
Can you ask art department (or yourself, if you do everything alone) “hey, you know that beautiful villa you made? well, it doesn’t work, make me a 1 storey hangar and put a couple of airplanes as we need something with two lateral lanes where players fight and something to block the middle” and then “hey wait, a boeing is too big, give me a cessna”, and so on.
I just cannot imagine any serious level design starting with 3d models (that’s also a reason why the autodesk engine interested me as you cna change stuff on the fly all of the time seamlessly between and UE).
As soon as you start testing and testing your level design over and over to offer the most balanced and funny experience the amount of work on your art department to change the stuff they’ve done starts being just too much.
It’s way easier to say to your art department “listen, you have a copy of the map with bsps, it’s been tested over and over and it works well, now concept artists and modelers find a way to make something pleasant to see out of these geometries”.