Yes they do, but not because it is a diuretic. The mechanism that stimulates muscles in the colon is different from the mechanism that pulls water and salt into the kidneys. The way diuretics impact bowel function is actually by taking water from the digestive tract, which does not cause people to need to poop. The muscle stimulation does that.

IIRC, diuretics make people pee, not poop. Caffeine stimulates the colon which makes people need to poop, which is unrelated to it being a diuretic. Diuretics can cause constipation because they pull water from the digestive tract.