This doesn't seem right to me. Given how the contacts are positioned deep in the socket, they wouldn't be reached if the plug isn't being inserted straight. Plus the ground pin is already slightly longer to mitigate this issue. Do you have a source for this explanation?
They are deep enough that it's not possible to make contact with the live and neutral pins before the ground pin. Try it, I just did and I wasn't able to do it regardless of angle.
