I did miss the part where neem oil is shown to be a cause for CHS. I did see speculation for what causes CHS.
Look I hope a cause and remedy is found soon, and that more correct information can help those affected. Truth is though we just don't know what causes CHS.
I'd be concerned that another condition was present, such as Cyclical Vomiting Syndrome. Would a doctor order the tests to rule out or look for other possible causes, or just tell vomiting patients to just stop using cannabis? It's not as if there is no bias against cannabis in many medical situations. It's also tricky to diagnose some digestive problems. Even something such as Crohns and Ulcerative Colitis can be difficult to differentiate ( and both can cause nausea and vomiting).
If someone thinks they have a problem with, or have health problems with, cannabis, I am all for them quitting, if it's what they want to do. If I thought it caused nausea and vomiting I'd quit. I would then expect the issues to stop, and be pleased if it did. I am also aware that there are various reasons for nausea and vomiting to be recurrent, and I would want to know the actual reason. I've had a misdiagnosis related to chronic nausea and vomiting, as did my daughter, and the wrong diagnosis costs time, suffering and health.
For my part, I am thrilled cannabis can control nausea and vomiting. I've relied on it this past month, and will rely on it in the future ( possibly this morning, as I am a bit queasy). It's good to know CHS exists. It's good to know it's rare, and that it's often misdiagnosed or self diagnosed. People are different, and if someone can't tolerate cannabis, I hope they can feel better soon.