You are correct, this is wrong. The rendering provider should be listed as such on the claim, when applicable. By not doing so, this could/would be considered fraudulent billing. While I understand the desire to treat patients is important, what the PT who owns the practice needs to understand is that it in order to be paid for that treatment by insurance, it has to be done legally.
One thing to be considered is that if the owner is billing everything under their name as rendering, an insurance company such as BCBS will eventually realize that the amount/time of services being billed in one day for "one" provider is more than they could actually do. I have seen this happen before, with a provider who was doing the same thing as you describe. Eventually they were audited, and had to pay back quite a bit of money.