I think it’s less about a ball recovery and more about the direction of the fumble for me.
In your scenario:
A fumble by a team that goes backwards and out of their own end zone should be a safety because anywhere else on the field a fumble that goes backward and out of bounds the ball is placed at the point it went out and possession remains with the offensive team. A team can’t snap the ball from inside their own end zone though, that’s a safety. The rule hasn’t changed because they are in the end zone.. it’s a safety because of the rule.
On the flip side, a ball fumbled forward out of bounds anywhere on the field always results in the ball going back to where the ball is fumbled and possession remains with the offensive team. But if it’s fumbled forward and out of the end zone, the rule suddenly is different from anywhere else on the field, and a touchback is awarded.
So when a ball is fumbled backwards, the rule is interpreted the exact same no matter where it is on the field. But when a ball is fumbled forward, the rule can change based on the area of the field. That’s the difficult part for me to accept. I have seen some decent points made about why the rule is correct and doesn’t need changing, but I just still don’t love it. Is what it is though, I don’t see them changing it.