First, you are correct that MKP is not a cult and everything you're saying here checks out with the research I just did into MKP.
What I meant was that it is cult-like in appearance. It's an engineered experience for human bonding and introspection. The members are doing stuff that's out of the ordinary and trying to connect to some deeper spiritual thing. Sometimes people get naked. There's a big wooden phallus used as a talking stick. There's a bunch of oversharing. It's not a cult, but it's not exactly Rotary Club either.
As far as roping you in, of course it's designed for that. The group couldn't grow without getting you to come back. There's a good chance you're going to form bonds with the other people in the group if you do a bunch of emotional stuff with them on a retreat. That's a social situation that I'd much prefer to avoid.
I looked at your HN profile and I see that you're a life coach for freelancers, so you might be less sensitive to what's triggering me about MKP. Don't take this the wrong way, but your site gives me a similar feeling as the MKP stuff. I'm pretty sure I'm your target too, as a developer considering switching to freelance work. I wish I could give you something more useful than "feels scammy, stay away", but that's how it comes across to me. And you're blogging about "mastermind groups", which also give me the same feel. It's possible that I'm just hyper-sensitive, but I think you'll have an easier time getting through to developers if you aren't tripping the alarm that tells me "this is a cult" or "here comes a pitch for an ebook".
As a side note, I wonder if you get many calls from putting your number in your HN profile. That was definitely noticeable and didn't trigger my overactive skepticism at all (even though it's obvious self promotion, it feels authentic).