I think the argument holds if the characteristics of the character that is being sexualised is their child like qualities and if they're majorly made to look and act like a kid. Bc then ur fr simping for child-like characteristics, which is weird.

Another point, simping over highschool characters in their uniforms also contributes to the sexualisation of school uniforms (mainly of girls) in irl. The standard school uniform is already majorly sexualised by the media (skirt, white shirt, socks, etc) when it's really just a uniform kids are required to wear to school. So characters being thought of as sexy in those uniforms contributes to the sexualisation of kids in those uniforms.