There is a saying that I remember from my not very impressive and ill-fated weightlifting career that, in a way, also applies to pitching or perhaps any athletic endeavor: You can be wrong, if you are strong.You all know I'm not a fan of bullet spin. Sorry, nobody is going to convince me it's a good thing. And I realize many people look at the pitchers on TV and use that as the standard for many things good and bad in pitching. But, I personally believe some pitchers are considered good despite what they do, not because of it. Cat Osterman is the best women's pitcher I've ever seen in person, none of her pitches were bullet spin.
The other point that needs to be remembered, that majority of girls that I know pitching on TV are very big girls. 6 foot, 6'1, 6'2, etc. Not even the best pitching coach in the world can teach a kid to grow to that size. Being that tall allows for a pitcher to get away with things that may not be the most mechanically sound. Pitchers today like to imitate Jordy Bahl. But, the previous generation of young pitchers wanted to imitate Monica Abbot. Personally, I've never understood or liked that giant bend forward she does prior to the pitch. But, she made it work no question. But would anyone encourage or teach their students to do that giant lean forward? Probably not, even though one of the best was doing it.
That is, if you are big enough, strong enough, or athletic enough you can have success—even great success—with mechanics, technique, or an approach that is sub-optimal or something an instructor would never teach because it would not work for mere mortals.
The girls pitching on TV for elite programs are the top 1% of pitchers in the country. You take the top 2 or 3 pitchers on a Top 25 team and you are talking 50-75 girls from across the country. They have unique physical—and most likely mental—attributes that exist prior to any discussion of mechanics. For those of them that have less than ideal mechanics or even poor mechanics, they simply have more room for error than your average or even above average pitcher.