A doctor can have practice rights at a hospital but not work for the hospital. So the OBGYN can deliver babies and do C-sections and such but isn't an employee of the hospital.
No they are just trying to draw a definitive line between the two entities. Doctors private practice vs the hospital. Probably for legal reasons but mostly for PR reasons. You know so they can argue that there was nothing to indicate Dr. Bebe Decapitator would decapitate a baby prior to actually doing so and that the doctor was very much a really real doctor that knew medical stuff so please don't make us pay lotses of money for the doctor doing a naughty.
Bullshit. I don't care what the legal definition of employee is, who authorized the doctor to work there? That's right, the hospital did. If the hospital doesn't want their reputation tied to shitty doctors, then don't let shitty doctors into your hospital.
Or your boss invites your estranged wife to just work there without telling anyone she's coming. Oh and then you hire the guy she slept with. And everyone is fucking everyone all the time. Including patients.
I swear, if Seattle Grace had an HR department they're probably all alcoholics.