This isn't about stopping Yuri from doing anything so much as it's doing something himself, so Otabek doesn't try to stop Yuri from touching himself. In fact, the arch of his spine actually gains a faster pace all on it's own, Otabek dragging him up and back down again more firmly, deeper, but letting him up faster, pulling down immediately. It's a lot like letting Yuri go back to riding him, but with that extra bit of force at the end of the drop.