The thing with Hubbard is exactly highlighting the issue. I think no one would argue that say Djokovic becoming trans and winning is a surprise - he already beats the men. But someone like Hubbard who is gifted enough to not be completely obscure, but not good enough to be world class either, that is exactly the person who can go from not winning to winning. Tiffany Abreu is another example, good enough to play 2nd division in the men's, but nothing special, then magically breaking records as a woman.
Yes, this is a good point. I see a lot of comments on here along the lines of ‘but what if Usain Bolt decided to identify as a woman? Would that be fair?’ Well, no, but Bolt is in a class of his own. Most men couldn’t beat Bolt either.
Someone in their 40s, who used to compete as a relatively ‘average’ competitor in the men’s events joining the women’s events and frequently beating women in their 20s...well, that makes a more obvious point.