Too much to read on that site, but I can say a few things about the INFJ-INTP relationship, beyond the other threads where I've talked about this.
With the INFJ-INTP there definitely is a benefactor-benefitor relationship, but it goes both ways. In any relationship the female has the caregiver role, whether they like it or not. In this case INFJ's are not good caregivers, but INTP's don't need a lot of care either, so the degree that the INFJ can muster (assuming a INFJ-female/INTP-male relationship) is more than adequate for the INTP. In my case she takes care of many practical aspects of daily life such as making sure we have food and doing the phone calls and such.
Getting into typology there is more, INFJ's have a tremendous appreciation of people, and a lot of that flows to INTP's who they just adore. I think my wife collects them, before me her best friend (still friends) is an INTP, she found me, and gave me an INTP son. She'll also search them out in public, such as Larry David who she hugely admires (he is absolutely an INTP). For me, getting this attention, respect and love is nourishing.
In the other direction, my analysis of the world and explaining the logical reasons for things is tremendously helpful to her. She'll come to me with something that makes her distraught, but I'll point out the good aspects of it and many times how it actually is a good thing. So I keep her on an even keel.
On the male-female side of things, while the female is the Caregiver the male is the Entertainer. Guys, if you don't use your sense of humor you'll never get laid (c.f. Christopher Hitchens). For the INTP it's imperative that we find somebody that can appreciate our offbeat humor, and in the INFJ we find the ideal audience. Both me and my INTP son come up with jokes that put her on the floor. The usual INTP fare will do, situational humor, taking things out of context, clever observational humor. INFJ's in particular get so traumatic and distraught that a highly developed and practiced humor will go far.
So to answer your question, for this relationship there is benefit going in both directions for different reasons. The symmetry in the INFJ-female to INTP-male is rather beautiful, as there are tie-ins and cross linkages that make it work quite well.
