Do you want to play your safeties deep on first down when Jared's been tearing up defenses, or use them to try to contain Gurley. Most defenses won't be able to do both.
Oh and re: the Falcons, they also had a LB who is extremely athletic who did a great job shadowing TG in the playoff game.
But yeah if I'm a DC playing the Rams there is no way I'd let them light me up in the passing game on first down. I'd definitely favor a cover 2 type look, would even go cover 3 if I had to depending on how good my safeties are. Gurley will still kill you (barring a great front seven), but that's infinitely better than being lit up for quick scores that put you down early. So in other words, most teams are now going to be afraid enough of Jared and that passing game that Todd Gurley is going to feast IMO.