To be clear, the report doesn't claim it's proven that trans women have no advantage in elite sports, but rather that the biomedical evidence is inconclusive and that the methodology of existing studies has been highly flawed.
It does go into some sociological factors which is good, and it draws attention to the fact that these studies are seemingly often conducted from a place of transphobia to begin with.
I suppose it's hard to do science on it as it's such a loaded topic, and the number of trans athletes is relatively small.