Except a "trans person" could just as easily be female as male.
The bone of contention isn't about "a trans person" or "trans people" generally competing in sports. It's solely about MALE people using claims of a trans gender identity to compete in the FEMALE category.
No one has a problem with females who are, or claim to be, "trans" competing in the female category - unless, that is, they've started taking exogenous testosterone or other androgens.
Two "trans persons" competed in the 2022 NCAA national women's swimming championships - one male (Lia Thomas) and one female (Izsac Henig). Objections were raised only about the male swimmer. Not coz he is, or says he is, "trans." But coz he's a MALE who had chosen to compete in the FEMALE category - and his muscling in was presented by some people as a good thing.
Since the vast majority of MS and HS-age kids today who've adopted a trans gender identity are female, it's likely that there are many more female trans-identifed HS students in Oregon than there are male ones. Chances are at least one of the female trans-identified students made it to the Oregon 2024 state championships and competed in the girls division where a male athlete who claims a trans gender identity won a girls' state title and ended up being booed for it by some in the crowd.
In CT this year, at least one prominent female HS athlete who competed and did well in the girls' state track & field championships has gotten press coverage for claiming to have a "trans non-binary" gender identity similar to Nikki Hiltz. No one took issue with that athlete competing in the girls' division. Most everyone wished her well. The only objections raised were about the two male HS school students in CT who were able to compete and win titles in the 2024 girls' state championship because they say they have a trans gender identity.
When male athletes claim a trans gender identity, it enables them to compete in a sex catgegory where they as males have an unfair advantage. When female athletes claim a trans gender identity, they do not get the same sort of benefit.