Indeed, I have recently run into this, too.
I think this reveals a logic error:
The window may display tracker help, or it may provide a form to select
among possible values. Which of the two it is depends on context (such
as whether or not the user has edit rights).

As the edit permissions aren't available from inside the help context
(at that point we don't know the originating item, only the property),
we can't conditionalize the display of form elements there as we would
do in normal item templates.
Thus, I would suggest to move this decision into the main item page
(where the help link appears), and then choose a different template,
depending on whether this is to be a 'help' display, or a value selector.