Good stuff. It really does appear that these things effectively do auto-overclocking. It reminds me of Vega. Get the cooling right and then set the lowest voltages you can to get the heat under control and then the magic happens.
It may well turn out that the best speeds will be a result of the silicon that can run at the lowest voltage at the base frequency and working out what that is will be the way to overclock rather than pushing higher fixed voltages.
It certainly bodes well for power efficiency and the future - wouldn't it be nice if every chip can effectively run near it's max ability and the ratings from the manufacturer become the minimum guaranteed speeds?
That way we maye also end up effectively paying for binning with the more expensive SKUs just having a higher guaranteed top speed.
Food for though at least.