Magaly, glad to hear your son is getting good intervention. Are you in Ireland? (Asking because you mention PHN vs Health Visitor?). I used to work in an ABA school in Dublin as a tutor.. many moons ago now..
Feeding/weaning difficulties can be subtly linked to many of the developmental difficulties, including (but not limited to) autism spectrum conditions. There are so many different types of difficulty that can result in difficulties with speaking and feeding, however, that it's hard to make any judgements beyong the fact that it is a serious concern.
IME the main reason that parents do not seek help in situations where there are obvious issues is grief, pure and simple (as if grief ever could be). Not everyone will react by denying, because all people handle these types of situations very differently.. but I have met many parents who have told me after diagnosis that they knew, in their heart of hearts, that something was seriously wrong but they wanted to scoop up their precious baby and head for the hills, hoping that would make it, somehow, not true. Others really don't know, like you Magaly. Others take it on like a lion and become experts on the subject in a very short period of time.. but these are just different ways of coping with something that is very difficult. So it's impossible to judge.
Harimo, not sure what is going on with your LO from that, really.. it could be something as simple as a quiet, calm personality or it could be his speech. I always say to everyone in this situation: get your child assessed. Most areas have waiting lists under control thanks to the Labour targets and nearly all have open door referral so it can do no harm..
The relationship between speech and social communication is a complex one, and can be reciprocal, but not always. I've met kids with severe speech and language disorder who remain sunny and sociable, kids who have become withdrawn because they haven't been understood and kids who have become behavioural.. and these 'outcomes' haven't always been related to the severity of the speech difficulty or factors like familial support etc. There is so much we don't know yet...