it was a bad overturn
if it adheres to the rule of completing the catch, the rule needs to be changed
IMO
I think there's another interesting rule at play here that was never considered-- forward progress.
IF we're going to agree that 3 steps constitutes a football move (and I certainly do) then we can take that bit out of the equation-- he caught the ball.
However, he was never able to make a forward move, he was being pulled from the moment he caught it, and so if we imagine an extreme instance of the scenario where, say, 3 other defenders arrive, literally pick him up, and shove him 5 yards further back, but he holds onto the ball, then this is where we typically see the officials spot the ball right where he made the catch. Because his forward progress was stopped. And even if a whistle doesn't occur immediately where forward progress is stopped, the refs typically treat ANYTHING that happens after that point, as a dead ball.
So IF we concede it was a catch (and I do), then we also have to consider that his forward progress could have been considered to be stopped, and so there actually was no fumble at all, and therefore no fumble return.
Which comes back to my 3rd most hated rule in football-- forward progress. I understand why they feel it's necessary to have such a rule, but man it is one of the most inconsistently called, subjective, POS decisions that refs can make in a game. And it occurs dozens of times in any given game, not just a handful like targeting or PI, so I believe its cumulative effect could end up being far greater than most of those one-offs.