It's still going to be problematic. There is a hidden selection bias that you can't get around. Eg in India there are still a lot of people that can't afford the CABG no matter how much it costs. Are those people less or more likely to die after surgery than the people that do get operated on? The answer invariably would be yes.

Do centres that do more surgery have better outcomes? The answer to this is already a resounding yes. There isn't any doubt about that, it's been shown over and over again for multiple different surgeries within developed countries. Surgeons knows this, and so do health insurance companies. But of course this has to be asymptotic. Doing 1000000 CABGs doesn't make you 1000 times better than the surgeon that does 1000. So I doubt there is any real difference between the surgical skill in Shetty's centre and top institutions in the US. It's an untestable question in any case. The important point is that the care overall seems grossly non-inferior to the US, not that the US is inferior.