Baby villagers walking through barrier blocks

I was working on my adventure map and I had some villager children in a house. There were just holes for windows, so I put barrier blocks in after seeing them escape. Later, I saw one of the children standing the block where one of the barriers was. I thought I might have not put a block there, but I checked and the hitbox was there. I don't know if this applies to adults as well because the hole wasn't big enough.