Nope, it’s just as an option for those that want it. They are making a version without the transmission part that directly connects to the drive shaft too. They have multiple EV designs going on and the vintage car crate EV system is just one of them.
They are also working on battery pack designs that mount where the current fuel tank is and looks like an original tank from the bottom. They are trying to make systems that fit with the design of the vintage cars.
I have an engineering colleague who worked on the original GM and Ford EV designs who is consulting for them. He gives me updates once in a while.