I appreciate you read physicians reports. I read my therapists reports as well (or talk to them in the halls). PM&R physicians do want do know what you're doing. Most others don't care as long as the patient feels better.
I disagree to some degree though about PT not being there to do what we want. Yes, you are a professional and the expert when it comes to PT, but when it comes to the diagnosis and pathophysiology behind the patient's injury, that's our domain. And it's yours as well if it's MSK-related, but we're still ultimately the ones responsible for the patient's care. We need to rule out more concerning issues. We need to decide what's absolutely or relatively contraindicated. And we need to convey that to you. If I send a post-fusion patient to you but forget to say what their precautions are, and then you have them doing cartwheels and somersaults and the patient gets injured, the patient may sue you. And then your lawyer is likely to point their finger at us physicians, and that's where the finger-pointing ends.
We prescribe PT just as we prescribe medications, and if we don't write down thorough instructions then it's the same as telling a pharmacist "patient has high blood pressure--eval and treat." Of course, if we trust the therapists, then we don't need to include so much detail. I write "eval and treat" for all my inpatient therapy orders. I trust them all, and if there are any contraindications I write them down. For outpt scripts I put more details in as the quality of therapy varies.