Exactly. I remember reading dating scene analyses that report the ratio of 2:1 for men and women around SF whereas in NYC it is just the reverse. This neatly explains the x2 factor.
Suppose that 42.5% of the population are women in a marriage or committed relationship, and then by definition 42.5% are also committed men. That leaves 10% of the population as single females and 5% as single males, and there's your 2:1 ratio for dating, created by just the small female surplus.
Would that hold for founding companies? I don't think so. Any of the 52.5% females could start a business, as could any of the 47.5% males. The small excess of women doesn't create a 2:1 ratio here. (There may be some correlation, that married and settled women are less likely to start a business, but the population ratio can't explain the entire outcome.)
There are probably significant demographic divisions (race, educational background, housing rent/own ratio, size of industry clusters, national origin, income distribution, etc) that probably have an impact.
Also, a high percentage of dating age people are in a relationship. If there is a 48:52 gender imbalance in 25-45 year old population. And 2/3 the women are in a relationship (ignoring the same sex relationships) the gender imbalance is more significant among the single population. 48 /3 vs 52 - (48*(2/3)) is 16:20 or 44.4:55.6