?ADMCMD_simUser= not automatically appended to URL for child page of page with FE group
?ADMCMD_simUser=<usergroup> is not automatically appended if page is child of page with FE group and extendToSubpage is set for parent.
- parent (FE group + extendToSubpages | -> child
If the parent page is loaded in frontend with view button, ?ADMCMD_simUser= is automatically appended.
I also noticed that in the 403 PageErrorHandler, the $reason['code'] is different in this case:
- for "parent": "access.page"
- for "child": "access.subsection"