I'm going to fan girl Hinch here, but EVERY child is different. I've mentioned in older posts that my eldest was so forward, bright as a button and wouldn't shut up from about 10 months old. My second was completely different, she didn't speak until quite late, she was one of those "bitey kids" at nursery as she lacked the vocabulary. I'm sure Ronnie is perfectly fine and will get there in his own time.
Also to add, Rex has 3 older siblings, he's surrounded by so much more going on than Ron. Hinch strikes me as a helicopter mum, whereas SS seems to just let her kids get on with it.