Possibly. He probably could vote by mail if he thinks to request a ballot, but he might think he’ll be out by election day, or he might not trust mail ballots thanks to the Fanta Menace demonizing them.
BTW, the thing with felons voting is state by state, so it’s not a universal thing. Some states allow felons to vote once they’ve completed their sentence, and I think there’s even a couple that allow felons to vote from prison.
As long as each of those ballots is filled out by an individual who is registered and legally able to vote, and is sealed by that person before it is handed off to whoever, I’m OK with this. I might rib them about their rank hypocrisy, but if they’re not falsifying ballots, they’re not really doing anything wrong.
Seriously, the idea of “ballot harvesting” is bullshit invented by people who just want to make it harder for people to vote because they’re afraid the people might vote against them.