You are correct, eggs are fine and my son has had Type 1 Diabetes since he was 17 years old and eats eggs daily for breakfast. Neither his Endocrinologist or the Dietician on staff has told him that eggs were not good for him.
Bummer for your son, but he’s getting excellent information. Type 1 is really nasty, since one mistake in applying insulin can be lethal. So, and I’m not a doctor (so keep that in mind!), I would always recommend staying away from carbs whenever possible for Type 1’s, which was the official recommendation before insulin was available (100 years ago)...still not enough, but people did live longer that way, back then. Now, with insulin available, if one eats as little carbs as possible, I suspect that just a bit of insulin would be needed to balance blood glucose...and that maintaining a decent level of would be much easier.
...again, just the peanut gallery here, but I am applying simple logic, which doesn’t seem to be in the capabilities of much of the medical establishment.