yeah now that ive thought about it its a good idea because a painted ballast isn't always grounded well and maybe it helps protect the electronics when theyre grounded better
We had a bunch of those ballasts in the church, some had the green wire, some had an aluminum wire on the ballast body instead...same brand and make but different dates...some were 1996 some were 1997
I think I have a cheapy T8 ballast with a green wire sticking out of it too. I think it was one of those T12/T8 electronic rapid start ballasts that came with a cheap striplight.
I vaguely remember seeing cheapo plastic cased electronic ballasts with a green ground connection for sale. The label said to connect the green wire to the fixture housing and ground supply wire. Didn't get it since i don't generally like electronic ballasts so forget about a Cheesey China brand one.