I did many many tests know and the system doesn't really make sense. I understand that you have to be crouching while using shadowy disguise (which is pretty dumb since you are invisible anyways but whatever)
but its not really consistent. What always seem to work is - crouch and wait until hidden and THEN activate the cloak.
I would be "ok" if I did cloak first and then crouch for hiding (again, which is kinda dumb idk) but this only works 5/10 times for whatever reason.
Its very frustrating.