I'm sure the narrative will be whether that play should be reviewable.
But honestly, I've never ever seen this play before. Been watching avidly since the early 80's. Never heard of it. Nobody on the feed mentioned it even minutes after the game was over. No players or coaches on either side argued it or brought it up. No refs even huddled together to discuss it. Nobody knew this was a rule. And most importantly, nobody even expected this to be even a potential foul.
The real question should be: Why should that play be a foul? I'd think that the burden should be proving why something is a foul. In this case, what justification is there to consider knocking a fumbled ball out of bounds illegal to begin with (and in particular why is this ONLY a foul if the ball happens to be batted in an end zone). It's a fumbled ball. Any player should be entitled to manage/handle or otherwise manipulate the ball in whatever manner they choose. It is a live ball.
Why is it illegal batting? Or rather why are players obligated to attempt to recover the ball in play as opposed to directing the ball out of bounds as can be done everywhere else?
If it's me, I'm dumping the rule entirely. It's just such a ridiculously rare occurrence, and it's also counter to how the ball is legally played everywhere else on the field. I could never see this event again in my life. If it's predicated on the 'Holy Roller' play, isn't the disallowing of advancement of a fumble by a player other than the fumbler by the possessing team enough to prevent that?
