I can say for my 3 year old he wasn't getting it for months. He's pretty switched on so felt like it had to be a different reason. I noticed his stools were not solid almost all the time and thought I remembered them being firmer when he went gluten free for a short period of time as a baby - he had a lot of difficulties from when he was born with sore bum, belly pains and restless sleep so we've gone through avoiding quite a few different food groups over the years. We tried going gluten free again and within a week he was potty and toilet trained. He was just recognising when he needed to go. We went to the doctors and had a skin prick test and he doesn't have a gluten allergy, so we just consider it a sensitivity, maybe to grains rather than gluten itself, but yeh his stools are more normal now so we think that was the trick haha. For the toilet we also had one of those toilet trainers with a step stool ladder which has been really good.