Partners in Crime
Do you remember which source these conclusions came from? Just intrigued, not implying that your source should be called into question. I more often hear that the INTP and ISTP are more complementary 'marriage material' for the ENTJ. Note that both have the T preference, as your F cognitive function is your last.
I only have two examples of ENTJs in my life, and our relations were (1) slightly awkward and (2) epic friendship. Our dynamics usually become a struggle for power, attention, and the punch line, because we both have more aggressive, extroverted approaches.
As for what we get from eachother-- usually just a good time relating Ne to Ni, storming the world with Te, and being an unstoppable force when tag teaming something. The ENFP does have Fi as an auxiliary function though (which is your last, oh no!), so I usually tone down the sentimental business when I'm around my ENTJ friends. This makes me think that both parties would have to work to balance out the Fi obstacle in order to make a relationship satisfying to both parties.
If nothing else, we make fun and challenging debate partners (who often love to par-tay!).
You know you've found an ENFP when they are equal parts silly/adventurous and thoughtful/intellectual. We're easiest to spot when in an extroverted mode, dominating conversations with less obvious puns and connections. As long as debate is kept light and playful, rather than what could be seen as an attack, your ideas will be entertained and appreciated by the ENFP.
Did that help? Don't overlook the ISTP if you're seeking potential relationship types! Sounds like INTP is your best bet, though.