I agree on the interrupt(since the only other heros with uninterruptable self-heals, those heals are either stationary(hog) or close to(76's heal spike allows a little juking, but not much room in that circle). All others are either an instant(Biotic grenade) or a passive(all passive heals).
But I'm not sure what else would justifiably pull bastion out of turret mode, except for Graviton Surge, and maybe Orisa's new pull ability, though I've not seen or played it, so I can't really take a firm position on that. Lucio's blast doesn't make sense, because it doesn't even move him in turret form, nor does junk's concussion mine. As it stands, you've already got rein's charge, hog's hook, and Sombra's hack(at quite a range and any angle, too) that knock him out, with two of those three physically moving him.
That's what I'm betting it is. Apart from the heal, I'd be suprised if Blizz made any big rollbacks before a month or so has passed, because they know as well as anyone that any big change like that tends to be greeted with cries of "Overpowered!"(if a buff) or "Made X completely useless!"(If nerf) by the community, until they figure out how to counter it. After all, they've been dealing with that shit since long, long before overwatch came about.