According to my own research it’s not possible that even younger alters would lose certain functions including speech and dexterity, processing, the ability to read. So this is why they may sound like a child but have excellent diction sentence structure and advanced vocabulary for their age, are capable of reading and getting around on their own. That being said it wouldn’t make sense there are alters who “don’t know how to speak yet”.

However having alters speaking different languages isn’t unheard of and actually happens all the time.