Do midwives act as if they are doctors, really?
I am also an Allied Health Professional and the reason we exist is that a GP can't be 100% up to date with research on all the many, many areas they need to deal with.
I am a speech and language therapist and I can tell you now that most GP's haven't the foggiest when it comes to development in this area: I have seen adults prescribed beta blockers to cure stammering, frenulectomies (tongue tie) suggested for lisps and, more worryingly, GP's telling parents of children who have significant social communication issues (read = undiagnosed ASD) that their 9/10 year old child will "grow out of it".
I have, of course, also come across fantastic GP's, but rarely have I met a general practitioner who knows very much about my specialist area.
Does a doctor know more about medical care and treatment of a vast array of conditions than I do? Of course. Do I know more about this particular aspect of child development (a niche within a niche within the range of things they must stay up to date with?). Of course!
The same is true for pretty much everything. A Community Paediatrician and a GP are worlds apart in terms of their understanding of children's development so I an presuming the same is true for an obstetrician and a GP.
GP's are the gatekeepers: they need to screen and decide on treatment on such a huge variety of issues from physical and mental health and well-being to child development, pregnancy etc. How could they possibly be as up-to-date as someone whose life's work it is to keep abreast of developments in a particular area?
OP, your post reminds me of a joke:
What's the difference between God and a GP? God doesn't think He's a GP.