Totally disagree. When you do that you now have to take all athletes and divide them by an arbitrary metric. DNA isn't arbitrary. It's clearly observable, relevant, and simple. Again, well over 99.9% of these issues aren't a matter of testosterone level, it's a biological male (XY) dominating an XX sport on their psychological whim.
You are wrong about the bolded part. DSD has been a much more prevalent issue over the last 3 decades in international sport. The transgender athlete is much more recent (last 5 years, or so), and there have been very few examples. Moving forward, as society becomes more accepting of individuals with gender dysphoria, I could see that becoming a bigger issue (we certainly hear about it much more these days). But to date, dealing with DSD athletes has been a much more common challenge.
I need to correct an error from my previous posts: I raised the issue of the masculinized XX female, and the need to protect the female class from their inherent advantages. As I look more deeply into this, there are no restrictions on a masculinized XX female DSD (typically from congenital adrenal hyperplasia) completing in the female class. So, that issue I raised is moot (point in favor of your argument).
We are in complete agreement that transgender women competing in female sport should not be allowed (at the highest level).