ICM
I’m having trouble knowing for sure what you asked, but I’ll try to respond to what I think you are saying.
First, let me say that it seems that secjay has correctly answered your question.
If I understand you, what you are asking is “Is it normal for some of the foreskin to be bunched up just behind the glans when I am erect?” The answer to that is “Yes, that it is normal.” You are correct that it is the frenulem that causes the extra skin to be bunched up behind the glans, as opposed to just hanging loosely along the shaft. As with most things human, some people will have more of this loose skin and others will have less.
I do not think that the frenulum would reduce in size as you mature. I do not expect that the frenulum would loosen its tension on the skin (on its
own) either. You can concentrate on stretching the frenulum and probably cause less of the bunching behind the head (but I’m not sure that you should). You’ll still have just as much slack space, but it might be spread out along the shaft.
I have not read anything about any method of shrinking the skin (short of circumcision) to have less slack. Since the skin is stretched much more readily than penis, anything you do in PE would likely cause you to have more spare skin, instead of less.
Again, although I do not know it for a fact, I believe that most uncircumcised men will have some slack skin right behind the glans when they are fully erect.
I do not think this issue gives you any clues about whether or not you are still growing, one way or the other.