In regards to the last anon. Yes the age gap seems to be big, but we don't know much outside of unnofical material like the podcast interview and such. For all we know Izel might be turning 14 soon in season or Yun could have barely turned 17. An age gap of 4 or 5 years isn't as toxic as people deem it to be when it comes to adolescents like both boys here. A similar example in fiction is the age gap between Aang and Katara in Avatar which was I believe 3 or so years.
Usually I don't like comparing AtLA with Onyx Equinox because everyone keeps doing it and it's tiring but I actually think you have a great point here!
I believe there is a tendency to oversexualize mlm relationships specially in western media. And a great example is Kataang.
As you mentioned, the age gap of Sang and Katara Is about 2-3 years. And I think people don't see it as "wrong" mostly because 1. The ship is heterosexual 2. The male part is the youngest and the one who's mostly flirting.
I bet if Aang had been 14 and Katara 12 everyone would have claimed the ship was horrendous and wrong. Specially if a 14 yo male started flirting with a younger girl.
Like you mentioned a 4 year gap between teenagers isn't as toxic as it might seem provided the oldest respects some physical boundaries and there is a lack of power dynamic which might put the younger one in a manipulative situation. Ships and relationships do not always mean sexual activities.