Resting a hand there is okay. When he's laying on his back, he will lightly place a hand while running his fingers through my hair. I actually like that. He said it's he's petting me for doing a good job. But I don't think that's what you mean.
For me, a hand on the head is okay, but not with force. Giving a little extra push to the back of the head is a definite no-no that results in a quick ending to it. It is for me to determine how far it will go in.
A boyfriend in my early 20's would use force on the back of my head. I hated it, but never fought him about it. I was inexperienced in orally pleasing a guy, he was my first. I allowed it because as he put it, he was "teaching me how to give a bj correctly". I never allowed anyone else to do that to me after him.