Another thing is culture. The in the company's where I've worked at, how the men talked about women was pretty off-putting to be honest. They didn't do it in front of women (obviously), but even your nerdy developers would drop comments that had me wondering whether I was really in the ckrrect field. I'm sure the women in those places notice that even if it's behind their backs.
You could argue about whether or not it's a good proxy for success, but your response sounds like you think women would be more likely to drop out of the field alltogether than men, which doesnt appear to be true
And I'd argue it's a pretty bad proxy. Because the field might be growing (or shrinking) and percentages don't mean anything. 23% of 10k is less than 20% of 5k, for example. The percentage numbers don't really indicate whether someone will stay in the field, it's just a number that's highly dependent on a lot of variables and a very bad indicator for "people are staying in the field". I'm happy to be corrected, it's just how I read this.
Additionally, if your assumption is that 23%>20%, that would kind of mean that it's capped at 23%, right? Once more the CS degree quota is higher than 23%, following your logic, that would be an indicator that women are more likely to leave the field because it naturally gravitates towards 23%. But that's not based on anything, you could argue just as well that it's an indicator that more women are starting to take interest in CS as a career.