You also make it sound like starting a business from home in your early 20's with kids is somehow more feasible than working a stable job. That doesn't really make sense, especially when you just talked about 90% of startups failing.
Baby requires too much attention and prevents work in normal 9-5 job with fixed schedule and meetings. But it leaves enough "holes" in time table to work on something.
Let's not undersell how hard it is to have kids when just starting out in life, when you generally have less resources, which may mean less stable housing. Couch surfing or staying with good friends for a week or two because of financial hardship problems is doable when you're single or a couple, it's much harder to swing with children unless you have very good friends in a more stable place in life than you or family. Requiring there be family means mobility is limited, and limited mobility means limited career choices.
That's not to say it's not a good idea for some people given their circumstances, just that it's not obviously a better or easier path.
This used to be common knowledge, and it was so for a reason. If someone doesn't want to go this route, they obviously have every right not to.. but they should understand the tradeoff.
It also used to be much more common for women to wed older and more established men. It also used to be less common for women to go to college. There are lots of societal norms that have changed to make early parenthood less popular than it used to be.
I worked very, very hard to build both a financially stable life and have a family "young." I had my first kid at 28, was married at 24, and am the youngest mother I know in my professional social circle.
The only women I know who had kids 18-25 had accidental pregnancies with flings or short-term nonviable relationships, the fathers bailed, and the mother spent many years living with her parents while struggling to have a much more basic career than those discussed on this board. None of them had time, money, social support, or educational resources as single mothers to "start a self funded company while working at home."
Ideally if a woman wants to have kids, she can make a plan to have them with a committed partner at sometime around or just before 30. If she also wants to be a start-up founder, frankly she should look for a non-traditional relationship where her husband takes on most of the childcare after those early baby months, and hopefully he also has a stable but flexible corporate or blue-collar job to give them a bit of financial buffer.
Your comment reminds me of those annoying answers on Stack Overflow that say: why are you trying to do that? you shouldn't do that! you should do what I think you should do instead!
90% of startups fail, they NEVER become successful. Gambling on some theoretical future success is just bad advice.
Also egg freezing and late age pregnancy is VERY expensive and complicated. Author herself had three miscarriages.
I would suggest something else: have children between 18-25, and start self funded company while working at home. By early 30ies, kids will be at school and company should generate some income.