I also set up something similar to what you did; we call them 'admin pages' or 'admin views.' In them, we mostly work with 'dispinclude' as it could lead to inconsistent configurations in cases where one monitored host is mentioned multiple times in different 'hosts.cfg' files.

My goal was to set up alert notifications based on 'PAGE=admiviews/user-a' in 'alerts.cfg,' but this does not work. My guess is that 'dispinclude' is indeed not designed to trigger alerts. Unfortunately, it would really come in handy in that case...