My husband seems to think my soon to be 6 month old is too small for his age because he's breastfed.…

My husband seems to think my soon to be 6 month old is too small for his age because he's breastfed. Idk how I feel about that. He's still wearing 3 month clothes (well 3-6 months) but he seems perfectly fine to me. He's super active, doing things well before he was supposed to (i.e.; sitting up at 3 months) and he has a great appetite. I don't think anything is wrong with his size and I definitely don't think it's associated with being exclusively breastfed 😔