but it's never going to be grounded, there isn't even a ground pin on the charger
If you swap in the extension cable head, that does indeed have a ground pin, at least in Australia anyway. The grounding comes from that metal ring that the connector uses as a guide. https://www.apple.com/au/shop/product/mw2n3x/a/power-adapter...
Apple sells a 3-pin extension cable
US Version: https://www.apple.com/shop/product/mw2n3ll/a/power-adapter-e...
If you swap in the extension cable head, that does indeed have a ground pin, at least in Australia anyway. The grounding comes from that metal ring that the connector uses as a guide. https://www.apple.com/au/shop/product/mw2n3x/a/power-adapter...