Agree with you that practice patterns vary and different things could make sense in different settings.
It's going to be predicated on community need.
I suspect that those of us most acutely aware of lack of medical oncology resources far from big metros are also those most removed from academic leadership.
We should always use the APP phenomenon for context. APPs are not physicians and typically come into an oncology career with no heme or onc background. They have mobile careers and may come to an oncology practice having done years of mostly unrelated surgical work, urgent care or floor medicine.
Typically, they are "onboarded" into oncology with some period of supervisory on the job training. Maybe 6 months?
Their clinical duties are highly variable once onboarded and in scenarios of dire medical oncology supply, can function fairly independently even in terms of prescribing chemotherapy.
Right now, in my clinic, I am busy enough. However, there is no doubt that I have felt the creep of marginalization over the past ten years. The medonc side of things is staffed more and more with APPs, with less patient continuity and with far inferior patient satisfaction than on the radonc side.
Frankly, I feel that medonc provides fairly low value f/u for most of our shared patients (do they really review imaging on their own like us or perform exams like us). However, the culture is for medonc to own the patient, and they are more often than not involved in long term, relatively low toxicity systemic therapy well beyond receipt of XRT.
Unless I'm scoping the patient or just can't bear to let them interpret the f/u imaging (SBRT lung and CNS cases), I end up letting a lot of these patients go.
At some point, taking ownership over metastatic or very high risk pCA patients, breast endocrine therapy and simple radio-sensitizing chemo will make sense for me and certainly for our clinic globally.
It will probably never make sense outside of training purposes in a big academic center.
However, academic places should consider that they may be training community oncologists on occasion. 
