In my world, there is no third date rule. There isn't any rule that dictates when I SHOULD be sleeping with a man. I will if I want to, and whether or not I do depends on how I feel about them. If a guy is pressuring me to get it on when I'm clearly not ready, he's gone. If a guy wants to walk away because he's not getting any and he thinks he should be, good, BYE.
A real man will know and understand that a woman should be treated like any other INDIVIDUAL. Meaning she has her own time line, her own priorities, her own likes and dislikes. Expecting that women will follow some preordained rule or risk looking like a prude/slut is incredibly immature and petty. If you truly like a girl you're dating and you find her to be worth it, then you'll stick around. There are plenty of other ways to let someone know you're into them without spreading your legs or dropping to your knees. Any guy that chooses to remain ignorant of that fact can keep walking.