My little boy had- last week, a very prominent bald spot atop his head. But now his bare patch is full of newly growing fur! XD Is this normal for young boys?

Is he neutered or freshly neutered?

Nope.

This happens to my two boys who are not neutered. Sometimes their little chest gland area does it too. Becomes very bald but always fills in again. Seems to happen when they are working really hard at scenting their surroundings.

He probably had a scenting marathon which caused his scent gland to look bigger.

I have also noticed that if there are no females around and there are two males, one will have a bigger bald spot than the other, usually the dominant male.

He'd originally come to me with sort of a 'gummy' looking scent gland- and when that fur fell off he had a nice clean looking bald spot, with no fur in it at all, but now it's been growing in fur again and is completely covered by a fresh patch of fuzz. I don't know if previously he just wasn't grooming properly -(Now he's meticulously clean.)

He's currently all by himself, and we don't have any other Gliders around for him to scent-war with.

I just found it a little unusual, because in the past when I've had Gliders, they kept their bald spot ...well, pretty bald until they were neutered. XD

With him being alone, he doesn't have a reason to get his testosterone up.

I believe that having a female around that comes into heat keeps their testosterone levels up. Kind of like deer.