If I've learned anything in ten years of paying attention to dating and relationships, it's this. People occupy a massive amount of grey area when it comes to this stuff. There are a lot of universal truths involving attraction, sex, friendship and dating. However, those truths can bend to varying degrees. I have been AFC, I have been "alpha", I have watched dozens of AFC's and "alphas" and everything in between over the last decade. There is no simple, singular answer. I know as men we want things to make sense so that we can act accordingly but people in general are pure chaos. This is why the best advice you see on these forums at the end of the day is simply to improve yourself. Be the best person you can be, treat people kindly, be honest, be authentic, and everything else sorts itself out. Seriously. Trying to make sense of an individuals behavior is almost impossible. There's far too much history, personality and day to day mood to truly understand.
Ultimately what you need to learn to master this part of your life is adaptation to individual people. Does no sex by the 5th date mean she's not interested? Does it mean she's damaged? Does it mean she's been raped? Does it mean she wants to be seen as wholesome? Does it mean she doesn't want to have sex with me? This level of micro analysis is useless so much of the time. If you get stuck whining about the fact people are complicated you will struggle a lot with life and particularly women.
This is why you decide what you want first, see if she aligns with your ideal, and just go date to date. You don't analyze, you just move forward and escalate. In between you improve yourself. The rest sorts itself out.
Don't get stuck wondering why. People are chaos.