My nephew was diagnosed with Coeliacs at 5yo but had no issues with diarrhea or bloating. It actually took awhile to get the docs to test for coeliacs (despite our family history) because of that.
I was diagnosed 5 years ago although it's likely I had coeliacs since I was a child but I showed very few symptoms and none bad enough that I thought there was something wrong with me. I simply thought it was normal but my mum was diagnosed with coeliacs and since it's hereditory we were all tested too. It wasn't until I went on a gluten free diet that these 'symptoms' which I thought were perfectly normal part of life cleared up.
My main issue was lethargy (but I didn't realise until I went gluten free and suddenly had all this energy). I was also malnutritioned for years which lead to me having bad nail, hair and teeth. Luckily the nails and hair regenerate, one day I hope to win lotto and fix my teeth.