By trimming things, like the fabric of his boxers being stretched tight, you’re turning down the intensity level of the picture.
With YA you want something a bit impressionistic. A little soft and fuzzy. So you want to focus less on graphic details and physical feelings, and more on the mental and emotional feelings of those new experiences.
I mean… why didn’t you just write about his natural lubricant dripping from the glans? His body was likely feeling that in the moment too.
Well because the devil is in the details. Right?
Each detail you add makes the picture more and more crystal clearly erotic.
Is the point of the scene to get people hot? Or is this moment more about building trust and intimacy between the characters?
And honestly if you were to query an agent and get signed, they might come to you and say that even what I wrote is too much for the publisher’s target audience and it needs to be even “fuzzier”