I think ENFPs (and most NFs in general) are all four humors
sanguine: optimistic, energetic, sociable
phlegmatic: chill, relaxed, likes to go at an easygoing pace
melancholic: deep, reflective, artistic, romantic
choleric: passionate, empowered, charismatic
personally, I don't find the 4 humors to be a relevent psychological tool
89% Extroverted ~ 68% Intuition ~ 84% Feeling ~ 89% Perceiving
Enneagram: 2w1 SO/SP Socionics: ENFp
Se 30.4% Si 19.1% - Ne 38.4% Ni 26.4% - Te 23.1% Ti 20% - Fe 46.4% Fi 35.8%
Sanguine | Phlegmatic
Right Brain Dominant
It's based on the notion that NF is Phlegmatic (in contrast to Choleric, which Keirsey claimed), and that ENP is Sanguine (Interaction Style).
For one thing, the five temperament version of the theory suggests that NF could also be Supine rather than Phlegmatic (or even a combination of both). So if you think you're not Phlegmatic, that may be why.
Since the first two only rank temperaments by relative "strength", then an INFP, which would be pure Phlegmatic or pure Supine would then see another temperament in second place, which might not fit the type correlation. (It also could be from a third area, called "Affection" as picked out by the last link). Likewise, since those first two only measure strength and not temperament area, then the combo might be reversed (between which is first and second), or the first one might pick out an INFP Supine's high need for people as "extroversion" and they could end up scoring high on Sanguine.
So while not perfect, it does seem the correlation works, one way or another.