Why? To put in a car that is not FSD? A car that can’t potentially replace 3 cars. That’s nuts I can’t believe he said that. All batteries are needed for Tesla. Let them buy salvage.
One reason that I'd like to see, is if Tesla finds an existing commercial truck manufacturer that would like to build commercial trucks with Tesla drive trains. Then Tesla doesn't need to create a complete commercial truck division, and all of the rest of the expertise and truck designs for all of the different flavors of commercial trucking.
Instead Tesla can stay focused on batteries, packs, and drive trains, while a partner does what they already know how to do - build the various variants of commercial trucks while having a plentiful supply of packs and drivetrains that they probably don't have expertise to build.
And that truck manufacturer will continue to provide service to commercial trucks (parts etc..), and also staying up on commercial truck regs, tools, and stuff that is also part of providing to that market.
Then again - you add commercial truck to Tesla's aspiration in light duty vehicles, and Tesla might need to be more like 4 or 5 TWh/year worth of cell/pack/drive train manufacturing.
Oh - and then you need to add in the Tesla Energy / storage aspirations, and maybe now you're more like 6 or 7 TWh/year.
Tesla has a very big horizon open ahead of it.