S_USER_NEW global template variable not based on Newly Registered Users group even though documentation states it is.

When using the S_USER_NEW global template variable it is documented to be basing this on the users within the Newly Registered Users group
Also see
https://wiki.phpbb.com/Global_Template_Variables#S_USER_NEW

However my findings are that it is actually basing this variable off the user post count instead so even if the user is still within the newly registered user group but has several posts this condition does not trigger or the opposite way around when the user is not in the group anymore this condition still triggers due to 0 posts.
This means that the documentation about it is incorrect or if it is supposed to be like this that the variable is incorrectly set.