I would argue that those are simplistic numbers that definitely don't take into account many other factors. But I'll give you one.

You're using a pros versus college comparison, which causes a problem for a good comparison. The players in the MLB are, in general, and typically the best of what the college has to offer. In other words, Felix Hernandez is facing a peer-level batters that are the best of the best. A counter argument is that Felix Hernandez is also one of the best of the best.

Bull is playing against players that are also the best of the best--of those coming from high school. The top to bottom skill level in a professional team is significantly smaller than that of a college women's team. That factor alone could explain any difference in that percentage. It is really a better top to bottom competition faced by Felix than by Bull.

You can't simply just look at a few statistics and come to some overreaching conclusion--there are way too many factors to do that. I go back to my original recommendation. Take a full spring, watch as many games as you can, and get to really understand that women's game. You'll be surprised at what you learn. Along the way, you'll possibly see a really dominant pitcher, like Keilani Ricketts was at Oklahoma, or you might learn about Dallas Escobedo, who as a freshman, pitched Arizona State to the World series, but only had average junior and senior years (although she is now on the women's national team). The fact is, when you watch a lot of games, you do get to see just how much of a team game it is.