On a pull or drop down, I never inform. They'd most likely call you crazy or get mad and no longer consider you. Even worse, if you later inform of non-redshirt during recruiting and then try to redshirt him, he may bring up the point about you telling him that you wouldn't redshirt him and then it will be near-impossible to redshirt.
I only do it on guys who I'd only take if they would redshirt.