I don't see how that was an AMC.
But to the issue of the article, I have had trouble understanding this. A surgery center is owned by some surgeons. The surgeons hire an anesthesiologist for wages. The surgeons bill for the "professional" services that the anesthesiologists had performed, rather than the anesthesiologist billing for them. The surgeons get the anesthesiologists payment, as well as the payment for the surgery.
What is the referral? Is it from the surgeon to the anesthesiologist? Is the kickback the professional fee? Or is it the wages of the anesthesiologist? Patients need an anesthetic in order to undergo a procedure. Shouldn't providing that be normal operating costs?