Fun fact, those two things go together. My oldest is autistic and needed several rounds of feeding therapy before he’d eat anything but Chicken Nuggets like 90% of the time.

if your constipation gets extreme enough your bowels start being unable to pull liquid out of what comes into them. So you go from being unable to poop at all to suddenly just having the still liquid stuff leaking out around the blockage being the only thing that can come out.