I'm not sure which doctor you mean, but it's an interesting approach that might possibly help people with food sensitivities, and possibly even prevent some cases of celiac disease from developing. I still wonder what might have happened with me had I listened to my allergist many years back who wanted me to only eat wheat once per week.

Apart from the symptoms of SIBO there may be other symptoms that you are unaware of because they come on so slowly. It takes a long time to fully recover, especially when diagnosed as an adult. Apart from the classic signs and symptoms, I had all sorts of strange ones that have gradually resolved including: heart arrhythmia, tendonitis, chilblains, body odour, painful scalp, memory problems and thickened red skin on knees and elbows. It is definitely worth getting a diagnosis and following a strict gluten free diet.

Here is more info about how to do a gluten challenge for a celiac disease blood panel, or for an endoscopy: and this recent study recommends 4-6 slices of wheat bread per day:    

To be tested for celiac disease using blood screening you need to be eating lots of gluten daily for 6-8 weeks beforehand.  This article might be helpful. It breaks down each type of test, and what a positive results means in terms of the probability that you might have celiac disease. One test that always needs to be done is the IgA Levels/Deficiency Test (often called "Total IGA") because some people are naturally IGA deficient, and if this is the case, then certain blood tests for celiac disease might be false-negative, and other types of tests need to be done to make an accurate diagnosis. The article includes the "Mayo Clinic Protocol," which is the best overall protocol for results to be ~98% accurate.    

I also just want to mention that it's possible that your doctor might diagnose him with celiac disease without a biopsy, because his score was ~7x the level of diagnosis, so it is worth having a discussion with your doctor about this approach.  In the Europe the new protocol for making a celiac disease diagnosis in children is if their tTg-IgA (tissue transglutaminase IgA) levels are 10 times or above the positive level for celiac disease. According to the latest research, if the blood test results are at certain high levels that range between 5-10 times the reference range for a positive celiac disease diagnosis, it may not be necessary to confirm the results using an endoscopy/biopsy: Blood Test Alone Can Diagnose Celiac Disease in Most Children and Adults TGA-IgA at or Above Five Times Normal Limit in Kids Indicates Celiac Disease in Nearly All Cases No More Biopsies to Diagnose Celiac Disease in Children!