@annie9824 Totally get it! I'm a bit busy at the moment getting the baby to bed and packing for a big trip, so I'm going to try to remember to come back later tonight and edit with more info and details, but I'll try to say something relatively short now.
So, I'm not a doctor, not in health care at all. But I am an attorney and have an MA in an area related to economic policy. My understanding is coming from a political and public health perspective. Back in 2010, Obamacare was passed, which led to a sort of national panic with the underlying question of: if medicine becomes more affordable, more people will want to go to the doctor, but we don't have enough doctors for all these people. What do we do? At that point and going forward, a number of state legislatures, particularly in Republican states, started to roll back regulation on NP and PA practice. NPs and PAs used to be part of a physician-led health care team, but state legislatures started to give them more and more practice authority, and you also started seeing insurance using terms like "provider" to refer to NP's, which has now trickled into the mainstream.
Prior to 2010, you basically wouldn't have gotten referrals exclusively from an NP without physician oversight since they weren't allowed to practice without physician oversight. Moreover, and then as exacerbated by Covid, we also started rolling back educational requirements for NPs. You used to basically need a decade or more of RN experience before an NP program would accept you, and in such programs, you were required to have a ton of hands-on experience. But now, requirements for have lessened and a number of online "NP diploma mills" have cropped up, which again, a number of state legislatures argue will fill some sort of gap, but these programs, in addition to lax admittance requirements, often don't require any in-person training, or barely any.
So you might still wonder, well, what's wrong with just taking up that NP on her referral? This is, I think, what is bugging me about the comments here, but I know it shouldn't since this isn't widely known. Basically, these comments are boiling down to, "well, it doesn't seem developmentally worrisome, but it's better safe than sorry, no harm from seeing a PT!" But is there no harm? I'm thinking here about negative externalities. It can be extremely hard to get in with a pediatric physical therapist, or really any, who actually takes insurance. In the US, specialists, not just therapists but anyone from neurologists to ENTs or what have you, can have long wait times for appointments, and be expensive. When you are taking a spot that's not really necessary, that's taking a spot from someone else.
Now you might think, "but that is just one person!" But the problem is, with growing NP independent practice and scope creep, it's not. For example,
studies referred to by the American Medical Association show that non-physicians order imaging at 400% the rate of physicians. That's just for imaging in the quickest one I could Google at the moment, but it's a common complaint across doctors and specialists, and even ER doctors, I know: they tend to get super wasteful referrals from NP's that would have been avoided had that patient been seen by an MD and not an NP, saving the patient significant time, money, and emotional stress, and allowing patients who actually needed those spots to get seen sooner.
In terms scope of practice today, it really depends on the state's legislatures, but I don't know a single MD who wouldn't be horrified at NP's diagnosing children, especially with something as silly as saying that a child needs PT for not hitting a milestone when the time for that milestone hasn't even been reached yet. That causes stress to the patient, wastes the patients time and money, (will they need to take off of work for that appointment?), wastes the PTs time, and takes the spot away from someone who needs it. At the very least, the OP should see a doctor first, as I am almost 100% confident that they would not reach the same conclusion as the NP based on what OP wrote here.
If you ask in r/noctor, they'll be able to give you a much better rundown from a medical perspective of why it's outside their scope of practice. I just gave the political summary of how it is only recently that such a thing is even legally allowed in some states.
Also, the reason for the MD shortage has to do with a shitty Congressional bill in the 1990s limiting funding for residencies, which basically limited how many students medical schools could take in per year, and has artificially shrunk our pool of doctors in this country. I'll find a link about that after dinner if you'd like to read more.