If you look at the breakdown of the Model Y with the casted front end and back end by Munroe on Youtube it's fairly modular, with a front end cast and back end

If you look at the breakdown of the Model Y with the casted front end and back end by Munroe on Youtube it's fairly modular, with a front end cast and back end cast both bolted to the battery pack in the middle, and the top of the car lowered onto the base. If one of these casts were damaged in an accident but the rest of the car was OK, it might make more sense to just replace the entire front end or back end cast with a new one.