It was too close to rule it the way they did. In every situation like that, you have to utilize the ruling on the field first, which was a touchdown, and go from there. If the TD call was premature, give it to the Rams on the half yard line. There was no conclusive evidence that he fumbled it into the endzone, so you just can't give the ball to the opposing team in that situation. The benefit of the doubt goes to the offense, or should.
That goes for any team. It would have been wrong if the shoe were on the other foot and the Rams were defending the goal line from the Seahawks.