What Mystery means by that is not that each girl is exactly the same, or that your pickup routine should be exactly the same. What it means is actually quite obvious, that game follows the following steps (see
http://www.seductionbase.com/mysterymethod.htm):
The attraction phase:
1. First you approach. That happens almost all the time, doesn't it? At least the two of you meet somehow.
2. You do "whatever" (call it DHV, offering value or whatever you like) to make the girl attracted to you. Because if she isn't attracted to you, you don't even have to consider the following steps. It's quite obvious when you think about it. Remember that attraction doesn't mean anything more than that she is at least interested enough to talk to you. You can kill the attraction at any time, by mistake or intentionally.
3. Investigate your own interest in the girl. Is she worth your time and effort? You always have to do this as well.
I don't think I have to continue, do I? These are obvious steps you have to go through no matter what. It's just the same with the rest. However, these steps are so general they don't really tell you anything. And the only step I don't agree with is S2 - LMR. It doesn't happen if you are good enough.
There is one thing to learn here that is quite good though - that you
always have to go through the
comfort stage. There are times when you are able to kiss the girl very early, and you may think you are "in goal" already and just need to go home with her. But that's not the case. You still need to do all your magic on her.