I know regarding development is pretty much frowned upon and Ive avoided mentioning it but......
My son is 8 and diagnosed at 7 with ASD and sensory processing disorder, this was a long battle! For 4 years I kept being told he was ‘The naughty kid’ by teachers, senco etc. I think what made them question if he needed a referral was the fact he hit his milestones pretty well, crawling by 6months, walking by 9, speech was always amazing he never baby talked, you could have a clear conversation with pretty well! It was just his meltdowns, anger issues and not being able to socialise with other kids then as he got older hurting others, climbing the school fence (at 6) walking out of classes, trashing classes, harming himself.
If he was how Ronnie was at his age I honestly think that would have helped with getting him seen sooner. Im not saying Im some expert and Ronnie is delayed but he just doesn't seem very ‘there’ Yes she does keep him in a lot of the time but I really don't think that would make much impact he should still be developing and showing a personality whether he is out at baby groups or not. My sisters boy was very much like Ronnie and he was diagnosed at 5 with ASD, I know thats young but he wasn't talking at all and would just make a constant noise.