About Gargos' command grab

I have been working on using Gargos’ command grab more frequently, and have noticed that when you do his shadow drain (forgive me, I have trouble remembering move names) the opponent seems to wake up at varying intervals, like sometimes it’ll be a hard knockdown and sometimes a soft one. I was curious if anyone knows why this is, or perhaps if it’s just a bug. Is there a specific trigger such as attacking opponent in the grab before the shadow steal vs skipping straight to the steal? Perhaps in combo vs out of combo?

I think it is a quick rise. The opponent can choose to stay down or do a quick rise.