I was born with celiac disease im 20 years old. And I've been gluten free my whole life. Yes my diet is 100 percent gluten free and no i don't eat at restaurants at all. I got glutened by a chips that was marked as gluten free but it wasn't the company said the packaging was old and the recipe was new.
Welcome to the forum, the biggest source of cross-contamination would be eating our in restaurants--even ones that have a gluten-free menu. If your son was just recently diagnosed I'd recommend trying not to eat out during his healing period, which could last up to a year or more, depending on how much villi damage he had.
How long ago were you diagnosed with celiac disease? How long have you been gluten-free? Is your diet strict, and are you 100% gluten-free? Do you eat out in restaurants?
Key word, "gluten-like".
By the way, have you looked up Dr. Osborne's credentials and his background? He is a licensed nutritionist but his scientific? medical? clinical background is that of a chiropractor. He is not taken seriously by many experts in the medical and scientific community.
If it is helpful to you to see these other cereal grain proteins as "gluten", I'm fine with that. The problem is, when you begin to promote that line of thinking to others, people get confused about what grains they actually need to avoid. About 10% of celiacs react to oat protein (avenin) like they do gluten (the protein in wheat/barley/rye). That is not news. But the vast majority of celiacs have no issue with these other cereal grains. If we start throwing around the term "gluten" to loosely embrace the proteins found in all cereal grains it's going to be very confusing to those just getting started who only need to avoid wheat/barley/rye. And it will also create a great deal of confusion in the restaurant industry trying to cater to that element of their customer base needing to eat gluten free.