I have a 14 year old daughter, almost 15. Due to her father’s side of the family’s genes, my daughter has been hairy since a young age. She has felt comfortable coming to me to properly groom and trim and I made sure she did that without shame. It makes her feel better and more comfortable and it’s not for anyone else.
Is it possible your son asked for that trimmer from his mom ? And that he went to her rather than You because your reaction would be “you don’t need it and no one is seeing anything down there anyways” and he might feel a bit shamed?
My ex and I have different ideas on certain things my daughter can wear. We both have rules and boundaries. And his can be kind of ridiculous sometimes ) daughter wanted a shirt that tied on the back but covered her whole front. I allowed it and she wears it with me . Not her dad because he said no.
Strange underwear for sure. But luckily they are “under” clothes. I don’t think anything is immoral here, just a little different .
How is your sons behavior ? That’s the biggest thing to focus on. Are his grades good? Does he drink, so drugs, stay out late, lie , treat women poorly? Is he a good kid? Are his friends good kids?