I don't get your meaning. Is it that immature people go for mindmates because mindmates make them feel good in the egotistical sense but mature people look for something else in a more mutual positive way than mindmates? If so, please explain.
Well... i've seen, and experienced myself when I was a teenager, relationships where one partner - typically the female - sorta takes care of the other's ego, you know? Holds back disagreeing opinions, lets them "be right" all the time, complements them a lot, panders to their pride and stuff like that, whilst the other person a) doesn't notice this, b) doesn't do anything similar in return and c) is often quite patronizing and critical of their partner, so it's a pretty unequal relationship in terms of "power" and perceived intellectual ability/value. BUT, because the female believes she can't do better, or is maybe blinded by the guy's good points, or too patient for her own good or any other reason, she carries on putting up with him. And the guy is so conceited and arrogant that he doesn't see any of this (maybe he has abysmal Fe), and thinks she's with him cos he's awesome, and that she agrees with him cos he's always right, and that he really is superior to her and stuff. And he thinks he gets on so well with her because she's the only one who really understands him - he sees other people disagreeing with him as them not understanding him, see?
And so, being with this girl makes him feel important and superior and great, but this is a bad side of himself that he doesn't like to admit to or is a bit of a blindspot for him, so HE thinks, or says, that he loves her for who she is, that she makes him feel good, that she's an equal and that's why he loves her, etc etc... it's sorta delusional.
You know, she says "oh he treats me like an equal and it's great to have a partner who's interested in deep conversations etc" to her friends, who are thinking "wtf? he's an asshole, he totally patronizes you all the time and thinks he's way above you intellectually", and the guy says "she appreciates my knowledge and we have great conversations, I really feel we're mind mates, it's great", to his friends who are thinking "yeah right, my ass, you just dominate her so she doesn't dare disagree and your conversations are mostly you talking and her agreeing and listening". But there's no telling either of them.
But I've also seen (and been in) relationships where it really is more equal, where the partners are rather more mature and self-aware, and they will defer to each other in sorta equally, half and half, and one partner treats the other with the same respect as they get treated. Where friends and family often comment in a positive way on how happy the pair clearly are and how well they treat each other, and people use them as an example when they're talking about great relationships that really work. And this sort of relationship is closer to being in reality what the immature version described above is thought of as, in the mind of the, frankly, douches in it.
Hope that helps explain what I had in mind... just thinking that someone with atrocious Fe and a sense of self-worth that's largely connected to their intellectual ability, would be particularly prone to this sort of thing. And, INTP would fit the bill there, potentially. I'm not saying at all that they're all like it, like I say, I'm just musing and theorizing