I think it matters in terms of psychological health. Internally thinking that an older teenager is attractive is a pretty normal thing that might happen to an allosexual human, whereas the same attraction for a younger teen or child is clear “get in therapy now before something bad happens” territory.

Please note that I have specified internal thoughts and not making gross conversation about how hot young people are and/or approaching them with sexual intentions.

But I agree that this is really not the context to bring up the difference.