Hmm…first of all: You are right…as always 
Second: So if this is the needed Syntax, then i can understand it, but don’t feel that i have read something like that in the docs…there was for template issues the passage with the |admin_urlname stated…or maybe i had a problem with the language barrier.
Third: With your solution, i get the desired admin-page, but it is not the same like i would access it right though admin-panel: (both screenshots are taken from same URL, first accessed via admin-panel, second accessed via template)…so looks like there is kind of lacking another “instance” info while accessing via template?
FIRST:
SECOND:
But THX again for your work 