If you look closely at the replay, the receiver seems to get both hands on the ball at the same time as the defender (left hand is somewhat hidden). The receiver’s right hand comes off but goes right back on as the players fall, and both players keep both hands on the ball after that. The ESPN drama queens read the rule, and the word “chest” is not in the language.
The ref may have made the right call. The call being that simultaneous possession happened when the ball reached the players, and continued long enough to call it as such.
According to the NFL rule book:
Possession: When a player controls the ball throughout the act of clearly touching both feet, or any other part of his body other than his hand(s), to the ground inbounds.
By that standard GB had procession and Seattle did not. Having a hand on the ball is not the same as procession.