Okay but that doesn't address why buying up the ETF would bid up the underlying, it just shows that a discount against NAV exists and Fed intervention could shr

Okay but that doesn't address why buying up the ETF would bid up the underlying, it just shows that a discount against NAV exists and Fed intervention could shrink it (just as my intervention could in my turkey example). Alternatively, the goal could be to do nothing about the 80 bps or whatever discount, but keep it the same while pushing up ETF share price and NAV together ... but I don't see why this intervention would do that, either.