This pair carries the oldest story in the subject: one presses, the other does not accelerate. Both of those are real and neither is a fault. The choleric raises the pressure because pressure normally works; the phlegmatic does not respond to it because the pace is not driven from outside, and pressing harder simply produces the same speed with more noise.
What almost nobody expects is the measure where these two are identical: persistence. Both stay with what they have taken on, and both are hard to move once they have decided. That is why this combination produces either an exceptionally durable partnership or an unusually long standoff, and why the difference between the two outcomes is almost entirely about how requests are made.