I have 3 children and have never heard of that!
Food introduction from 6mths + yes bit not gluten.
You are usually recommend to start of with rice cereal (least likely to cause allergic reaction) the puréed fruit & veg (in order of least likely to cause allergy, something you'd have to look up as my youngest is now 6 years, I think I stared with apple)
I didn't really start bread until 1year old. My kids never had teething rusks (hard bread). It's up to you.
Celiacs is genetic, if your baby has it, it's from birth. Gluten intolerance can be caused by to much gluten, among other things (can be a small genetic component in there too)