This is what the warranty says, specifically:
"Warranty limitations
This New Vehicle Limited Warranty does not cover any vehicle damage or malfunction directly or indirectly caused
by, due to or resulting from normal wear or deterioration, abuse, misuse, negligence, accident, lack of or improper
maintenance, operation, storage or transport, including, but not limited to, any of the following:
-Using the vehicle as a stationary power source"
That just means if you're using it as V2G or V2H, anything that's damaged isn't covered. That makes sense because in V2G mode, you are directly exposing the battery to outside the car. If you're using a V2G inverter, any malfunction of it could damage the battery. One would hope the V2G device's warranty would cover any damage it might cause.
I think Tesla's current "V2G" strategy is the PowerWall, now. But, they could develop a Tesla-specific V2G inverter that would have end-to-end warranty coverage. It would be great to be able to charge up at night, then allow the car to drain down to 50% or so providing power to the house.