I remember the odd time in the old days getting a via Manchester Central Zone ticket to say Bolton and being told you had to travel via Metrolink. One instance was future advisory and one was an argument, If I recall. Either way I never went by Metrolink or bought the higher any permitted / Manchester fare ever in my years travelling, though I don’t think I ever bought one after switching to e tickets or on a physical ticket with an Aztec, as I didn’t have reason to do one of those journeys that were route Manchester Central Zone.