Openly and directly speaking about one's desires for example isn't an easy skill.

That's a higher-level skill though. What makes this possible in the first place is having a secure and well-defined "frame", which is an intended result of pursuing what you call "lower vulnerability". Perhaps the term "vulnerability" is simply too ambiguous.

If a woman touches you, do you tense up or do you relax? If you tense up because you are afraid of intimacy, it's going to make connection harder. It's even worse if you engage in physical contact because you read on the internet that you should and then tense up because you are afraid of physical contact.

You're right about this pitfall of physical contact; somewhat ironically, this is one thing that can be easily spotted and addressed by an actual PUA coach, while it's really hard to self-correct on one's own. You say that PUAs seek to "maximize bootcamp attendance" and this makes their free advice less than trustworthy, but that just doesn't reflect my experience. There's quite a bit of annoying commercialism, but overall development of the community largely occurs through free-ranging discussion.

There are many sources for improving social image and attitude.

Sure, but how many of these sources are as clear and (loosely) empirically based? (One of the tenets of PUA is A/B field testing of every innovation: this is the actual underlying reason for their focus on the unforgiving bar- and club-environment. It's not about making it harder for newcomers and selling more bootcamps - that's just a convenient side effect.)