Someone wasn’t being honest with their physician then. While CHS is rare the symptoms are quite different especially for severe cases of gastroparesis. CHS occurs quite randomly and we have no idea why it effects certain individuals but if someone stops taking cannabis for 7-10 days their symptoms completely go away. Should be one of the first things a physician discusses if someone presents with those symptoms and admits to being a frequent cannabis user.
It has to do with overstimulation of the TRPV1 cannabinoid receptor. That receptor is in charge of regulating gastric functions and is stimulated by cannabinoids and capsaicin. The working theory is that the receptor just wears out with tolerance buildup. This is why it rebounds when you stop using weed.
Also, in theory you could get this condition from using CBD. Its not about THC, all cannabinoids can cause the condition.