The only angle we can see shows a tackler going at Gurley about where they spotted it.
Reynolds and a Seahawk are in the way of the live camera angle so you can't get any idea from that whether Gurley's knee might have gone down.
But just my longtime fan eyeballs tell me that if he had been tackled where they spotted it, he would have SLID to where he stopped.
He didn't slide, he fell forward a good yard across the 1st down mark. I don't see how you can fall forward that far if your legs are already down.
Anyway, Fox had some game summary graphic that they were bound and determined to show and talk about, so they refused to show any replay, and/or from a different angle.
The real question is why the booth didn't ask for replay on such a critical, critical spot.
Could have cost the Rams the game, but happily, it didn't!
Ramily!