In my experience, self-close fridge doors have a graduated spindle screw hinge: as you open the door it is slightly elevated via screwing upward on the hinge, then gravity forces the door to spin in the reverse direction when you let go. This works fine and closes the door if the fridge is tilted back at the manufacturer-specified angle (i think like 3° usually?) via adjusting the front feet/supports. But if the fridge is tilted too much or not at all, it either won't work well or will be unable to close completely.

Tl;dr: generally works if you follow the manual.