Yes Spinach does make you poop and Spinach is also good to eat when you're having trouble moving your bowels or have constipation.
Spinach is pretty high in fiber which helps make people poop since the more fiber you consume the more you usually have to poop.
Aside from fiber Spinach also contains magnesium and both fiber and magnesium help to flush your colon out so you actually get a natural colon cleanse and you benefit your health from the fiber and magnesium as well as the other nutrients that Spinach contains.
You can also get diarrhea when eating too much spinach which happened to me one day when I was loving Spinach with some cheese on it and then I overindulged in the cheese spinach and then I had diarrhea for a few days after that.
But when eaten in moderation the Spinach is very healthy and helps you poop and cleanses your colon.