Truth be told, I’m 28. I didn’t claim that 90% of all MO women are married by 23. I said 90% of my graduating class.
There is a trend for RW MO kids who go to RWMO/Charedi-lite institutions in Israel to go RW/Yeshivish. But IME, the older the Yeshivish oriented women get and remain unmarried, the more likely they are to become MO and move to the UWS. My sister is in her early 30s and all the girls from her HS BY class who are still single live on the UWS and are no longer Yeshivish. I think this has to do with the fact that the older a non-married Yeshivish girl gets, the more educated/worldly she gets, whereas a non-married Yeshivish boy stays in Yeshiva. So she starts relating more and more towards the MO crowd whereas he is just likely to marry someone much younger, much to the disdain of AZ.
Again, just my experience.