I'm sure it's happened before, but I can't really remember a situation where a guy caught the ball in the end zone and got both feet down, then dropped the ball after the fact without going to the ground. I get the idea that "between the endzones, you have to get two feet down, and make a football move, so therefore, the same applies in the end zone" but making a football move on a play where the play basically ends once you get both feet down is just weird. Just a really weird and rare situation that happened yesterday.
The real issue was Landon Collins dropping the easy interception, and there was seemingly another clock issue with 2:10 left in the game that seemed to allow the Patriots to save 40 seconds of the clock.