@RIOT: Graves Can Move While Snared?

I just recently played a game with a Graves on the enemy team and a Lux on my team. What had happened was that Lux snared Graves as Graves was attacking Lee Sin. Lux proceeded to ult Graves but Graves had used his ult to jump backwards out of Lux's Ult... while he was snared. I understand His ability to jump backwards from his ult, but shouldn't that render the ability to not work since it allows him to move while snared? I do believe that other champions with mobility spells can't be used while snared. Is it possible to just let Graves use his ultimate without jumping backwards while snared? It was a problematic experience when it happened during the game and caused a winnable play to crumble horribly. And no, the snare duration didn't wear off nor did he have any tenacity. It was an instant Q,R combo from Lux when this had happened.