The UK/Ireland 3 prong duckhead is grounded. I have no idea why third parties haven't produced grounded versions, other than the obvious (no demand and anyone who cares has a solution, use the extension cable).
It is most certainly not. The ground is done over the round pin that slides into the duckhead. If you check the rail where the pin slides in, it's all plastic.
The extension cable is the only one that's grounded.
[1] https://www.amazon.com/Replacement-Adapter-Duckhead-Universa...