Again you are wrong. On a catch he has to establish possession. If he was a runner as you suggest the minute a player touches him would be ruled down (knee touching) so impossible to fumble.
I disagree. Because he was in the motion of falling to the ground, until he finishes landing with clear possession it's not a catch. This is based on the current rule, not feelings of what the rule should be.
The rule is saying that the only reason he didn't establish possession was because he fumbled it when going to ground.
But let's say he didn't lose the ball as his arm slammed into the ground. Instead, a pats plats poked the ball out of his hand, as his elbow and forearm were on the grass. What would be the din? The entire "Fumbled while going to the ground" idea is erased, as that never happened. So we would look to see if he establishes possession before the forced fumble. He gets a knee, two feet and a forearm down in bounds. He established possession. We would then say the ball crossed the plane before the forced fumble and it is a touchdown.
In other words, landing on the ground and fumbling RETROACTIVELY undid the catch. That is incredibly stupid.