On help page of data.stackexchange, It is stated that:
The ##UserId## parameter is treated specially for users who are logged in. If they have an account on the target site that shares the email used in their Data Explorer account, their user ID on that site will be automatically populated.
Automatic population of ##UserId## fields when possible (if you have a matching email)
This is no longer true. As per Why is the ##UserID## parameter not populated in Data Explorer anymore? this bug is by design as a result of the removal of Gravatar hashes for user privacy. So I think help section should be updated.
PS: I know that SEDE User ID Autofiller can be used to resolve this issue. I am wondering why this feature hasn't been natively implemented as stated in the help section?