namespace "winrt::Windows::Foundation::EventRegistrationToken" has no member "EventRegistrationToken"

I am using Windows SDK version 10.0.17763.0. Based on https://learn.microsoft.com/en-us/uwp/api/windows.foundation.eventregistrationtoken, EventRegistrationToken has been introduced in 10.0.10240. So I am confused as to why I would get an error when trying to use it. I also don't see it defined in the Windows.Foundation.h (10.0.17763) I have.

The comment from Raymond Chan is the answer:

::EventRegistrationToken is the ABI name. winrt::event_token is the C++/WinRT name. It sounds like you're mixing the two.