You have to consider that any AI content worthy of the Oscar shortlist is going to be very high-quality, and likely intensely hand/human-tweaked in the first place. It's not from the general population of all AI content out there.

> I have always heard that dopers are consistently ahead of testing regimes

I don't know about that, even the very biggest names with the most funding quite often get dinged for it. I suppose I'm not really saying that the detection rate for doping is high, though, just that it's much higher than AI detection in high-quality content (which I would suggest is approximately zero).