If you think diagnosing something as anxiety is the same as dismissing that person's experience and suffering and need for help, you're part of the problem.

Your entire argument only works if you accept the premise that this condition stems from anxiety alone. Since you have accepted this with what appears to be near certainty, then of course the rest of your argument makes sense to you, and your diagnosis of anxiety probably feels compassionate and sensitive.

To a person who does not share your confidence that anxiety is the only factor in play here, your dismissal of other possible factors is crazy-making.

Just acknowledging that there might be a factor here we don't fully understand would be enough. It's fine if anxiety is the best diagnosis and treatment plan given what we know right now. But the certainty that it's the entire story is off-putting.

You said yourself that depression/anxiety for physical symptoms are "diagnoses of exclusion, coming long after everything else has been exhausted." They are a fallback when you don't have another explanation. So why do you present a fallback diagnosis with certainty?

Nobody is saying that at all. The physical causes should be investigated, obviously. Suggesting to the patient that it might be psychological is not "dismissing" anything. Of course, it is true that most patients are vehemently opposed to the idea of psychosomatic pain, as well as many/most doctors. John Sarno's books are a fascinating read.

In this case there doesn't appear to be any pain, or physical sensation at all. You can't sense a "hole", any more than you can sense inflammation or the like.

On the other hand, if you want a really mind-expanding read about the fuzzier edges of medicine, you might want to read Daniel Moerman's "Meaning, Medicine, and the 'Placebo Effect'." Don't let down your skeptical guard, but it's worth a read.