The idea is supposed to be that your Mag can help you out offline when there are definitely no other players around to revive you, whereas online it isn't necessary, because you should have a teammate around to use Reverser. On V2, Mag revival is based upon your Mag's activation rate, so a smart Mag such as Soniti revives you something like 30% of the time. Sega greatly nerfed this on GC (and seemingly tied it to your level, so when you're a low level, your Mag is more likely to revive you than when you're at a high level) and reduced the rate to more like 1% success. Even if it were fixed on BB, the ability is almost completely useless, so it wouldn't make any difference. It's not as though you can run around without Scape Dolls because you know your Mag is going to save you, because it probably won't, even on V2 (although there is a decent chance that it will spare your Scape Doll now and then, unlike on GC).