I agree with you.
And I've had a child who had a genetic disease that affected their weight. In our case it was malaborbsion, and we fought to get as much food in as possible, including allowing fried chicken nuggets dipped in butter, because we needed as many calories per ounce as possible. Like the exact opposite of a diet, and we could never get above weight, because of the disease. We ended up with a feeding tube going 24/7.
I've seen way too many people allow their kids to eat like we struggled to get ours to.
The diseases that cause weight issues are not nearly as common as weight issues.
(Have another child who ate normally like the rest of the family, and is a normal weight. Actually, kind of on the skinny side, but without a lot of effort)