Preselection works because it gives women additional testing data

When other women have already been around you and stayed, it acts like extra data points in a woman's assessment of you. It is not just that she has tested you herself. Other women have tested you too, and they stuck around rather than leaving after the first encounter. This layered evidence lowers a woman's anxiety around you, and lowering her anxiety is essentially the whole goal on a first or second date. Until that anxiety drops, physical intimacy will not happen. That is simply how it works.