Yes, AGL is one of those vertically-integrated gentailers (as is Origin, and Snowy Hydro).I assume AGL (who also owns OVO) can consider their production cost of electricity rather than the actual NEM price whilst pricing these plans.
I don't think it's altruism, I think that they've found that EV owners tend to be higher electricity consumers even when not charging their EVs, so they can afford to give some cheap overnight charging to attract that business.