It already does, and in more detail:
What it doesn't do (AFAIK) is use those tendencies to determine how to pitch you over the course of your career - it doesn't carry that data beyond the game you're playing in, in other words.
Then again, given how upset people get about the CPU "cheating" and such, allowing it to have a "book" on you may not be the best of ideas.
Also, I'm pretty sure it tracks many more than 6 PA's - this screen is from early April and I'm not sure the guy HAS more that 6 PA's. This is the Locker Room screen from the RTTS menu, if you still have the game you can see the screen for yourself.