Last night was yet another addition to the 17 year (and counting) thrill ride that is the Brady/Beichick Patriots. I dont really care if anyone hates the call or thinks it's the wrong call or thinks it's an NFL conspiracy, the Pats pulled out the miracle and the ride continues for now.
Objectively, I can't fathom why the rule book would make that a 'no catch'. My eyes tell me he caught it, controlled it, held it, stretched out, broke the plane and scored. But I'll gladly take it. What a great game.
There is a very good reason for it.
In your scenario a guy could "catch" the ball, immediately go down, and so long as he crosses the plane before he loses control everything is good.
But this opens up a whole can of worms.
What if the ball flies wildly out of the receiver's hands a split second after he crosses the plane? Did he truly establish control if he can't hold on through that simple action? What if he briefly looked like he had control but really didn't? How short a time does he have to have it before he touches the plane for it to count?
The current rule removes all this ambiguity. After a reception you must control the ball all the way through the ground or you don't receive credit for a catch. It doesn't matter what part of the field you're on. Just hold on to the ball all the way through the ground. It's the player's responsibility to know these rules and follow them.
If the Pittsburgh receiver had just barely crossed the plane after the catch and then lost the ball in mid-air and still gotten credit for a TD Pats fans would be livid.
Truth is that football is a very tough game to officiate, and someone is going to be angry every time. Like on that 37-yard reception by Cooks that was called back because he was shoved out of bounds and was the first to touch the ball. He really only had one leg out of bounds for half a second before he jumped back in, and still it was enough. He beat his man but lost the reception due to a technicality. It didn't "feel" right, and yet there are good reasons for the rule.
The best teams - like the Patriots - know the intricacies and use it to their advantage (Malcolm Butler's goal-line strip-fumble earlier in the year for a touchback is a good example). The others are left with excuses and conspiracy theories.