My EV (not GM, not Tesla) has a 10 year / 100K warranty on the battery and other components that would be like a drive train warranty on gas cars. The warranty guarantees a linear degradation of battery range across years to 50% range in the last year. Most EV's have a battery warranties like that. Mine so far has no noticeable range degradation (4 years, 86K miles).
However, my solar batteries for the home have a much different warranty: 7,000 cycles (one per day = 19 years). And their suggested top charge is 100% (not 80% like most EV batteries) with the similar discharge floor (suggested to stop at 20%, so 80% discharge daily). Even then I wouldn't use solar batteries to sell power to the grid unless the payback was extremely high per kWh.
At best I'd get 1/3rd of what it costs me to buy per kWh (4.9¢ / kWh on weekday summer afternoons, vs 15-16¢ / kWh when I buy power from the grid, after paying fuel surcharge rate and state tax). Even then there are extra fees for the privilege to sell power to the grid. For just about anyone it's best to just not sell power to the grid, not pay the extra fees, and just reduce how much power you pull from the grid overall. Since an EV battery isn't an external source of power like solar, just keep the charge in the battery for tomorrow's trip.
Nothing more than useless marketing angle