Me (an average male basketball player) playing against the best female basketball players in high school and jr high and dominating them is absolutely true. They had no chance against me.
As for the average male not being similar to the average female in physical nature google agrees with me. Average male is 5 feet 9 inches and 197 lbs. Average female is 5 feet 4 inches and 170 lbs. Those height and weight disparties would never be allowed to box or wrestle or compete in mma against each other for a reason. That doesn't take into account the other differences such as coordination, leaping ability, strength, speed, etc that the average male is also superior in comparison to the average female.
Yes, average male athletes are much bigger than average female athletes. No question.
Same reason we have size restrictions in pee wee football as kids at that stage have large physique differences at that stage. Larger kids are line only to protect the smaller players.
The trans women that are winning women's competitions would not be competing at near the level if they competed against biological males in the majority of instances (i.e. the trans weightlifter in the olympics would be leaps and bounds below the mens minimum qualifier). I'm not even sure how someone can argue against this with a straight face.
By middle school and high school it begins to even out, and tryouts tend to weed out the less athletic folks, at least in the bigger more competitive schools.
And as competition increases (college then NBA/WNBA using bball as any example) the top athletes rise up. WNBA women simply cannot compete against NBA men physically. There is a reason only one woman was ever drafted in the NBA (by the Jazz) but never played.
These same characteristics flow through to lower levels of competition.
If It becomes the societal norm for biological males identifying as females to compete in women's sports, on average these trans athletes will have a physiological advantage over cisgender females, and you'll see it at an even greater rate.
Right now I'd guess many trans athletes play in their biological sport for many reasons, societal pressure and discrimination being a key driver.
I'm not sure who is pressing a narrative here that a trans person is trying to fool anyone. I think they are dealing with a difficult phsiological/psychological issue where their brain and body don't jive. That does not mean cisgender females should be penalized or lose out on opportunities like scholarships, etc.
We all know the suicide rate for trans people is sky high no matter how much support they have (I can't imagine what I'd feel like if I couldn't indentify with my biological gender). Whatever side someone is one, we should all agree that this group needs love and support, even if many disagree how that support should be supplied. I think we can be respectful of everyone's rights without enhancing or taking away rights of others.
That said, I don't think cisgender women athletes should necessarily lose out on potential opportunities whether it is playing time, scholarships, etc. And ultimately, they should decide, not me.
An open division makes more sense to me.