I closed previous report, because you didn't provide any proofs and i don't see any in this one too. It's just your opinion on how it should work.
If cd will reset on 2nd grip, it makes possible to abuse it for infinite grip.
Let's say target X has immune. So, you can use grip on someone else -> use grip on target X (cd will reset) -> use grip on someone else -> use grip on target X (cd will reset) -> use grip on someone else -> etc.
Is that how it supposed to work? It makes no sense.