Anxiety and depression are the most common (commonest is not a word, MD) mental illnesses in the world, not delusion disorder. Delusions can be a symptom of anxiety and depression, but this does not mean that delusion didn't cause a physical symptom. Again, in the very common case of anxiety and panic bringing people to the ER with heart problems, it's a mind problem causing a heart issue. If the mind problem is not treated, it can continue to physically affect the heart. This does not mean the heart problem was never real, but the mind was plagued with so much anxiety or panic that it causes a physical effect. Your mind is tricked, but that trick results in actual physical results that can be seen on EKGs and in your vitals. To claim that because a delusion must mean the patient is making up everything in their head and therefore even the physical symptoms are not real, is unhelpful and dangerous. It's especially unhelpful when it is not even properly explained to the patient how anxiety can cause these symptoms.

I'm sure, random redditor with questionable grammar who quotes a wordpress blog as evidence, I'm sure you used to be a doctor. However, doctor who insist they must be right because they are MDs, they are accredited, and therefore they are Smart and should be believed can really do more harm to their patients than good. In current practice, evidence based practice is used and built on, and we acknowledge that what we know about things like anxiety have greatly evolved in the last 10 years, let alone 40. Psychology is an ever-evolving field, and to effectively understand and treat patients, you must evolve with it.