Why is it obvious Lin YuTing has XY chromosomes? She was registered female at birth, raised as a girl, has always competed in female categories and the only allegation she has XY chromosomes comes from a Russian boxing official which has no credibility since it is no longer sanctioned as a body by the IOC and the Russian state has a long history of spreading misinformation around gender.
She may have high testosterone levels. That can be caused by a variety of hormonal conditions that affect women including CAH and PCOS, but would not suggest chromosomal differences. Lin Yu Ting has never identified as either intersex or transsexual.
Even if she has high testosterone levels the IOC requires these are controlled for people to compete in the female category, i.e. she must be taking medication to keep them under control, so the fact she has once failed a testosterone test does not mean she currently has high testosterone levels giving her an unfair advantage in the female category.
The geopolitics of this are obvious - it's Russian misinformation designed to undermine the IOC because Russia cannot compete. Probably compounded by China as she is Taiwanese.