From the conditions of use, paragraph 5.2:

An Interrail Global Pass may only be used for two specific trips in the country of residence of the traveller (provided this country is an Interrail participating country). These two trips are referred to as the outbound and inbound journey.

• The outbound journey can be used to travel from any location in the country of residence to the border or an airport or port.
• The inbound journey can be used to travel from the border or an airport or port back to any location in the country of residence.

During these trips, the traveller may travel with more than one train, provided the trips are within the same day. Please note that the special rule for travel with an overnight train also applies.

So they don't specify you need to take the shortest or the fastest way to a border, airport or port.

On the mobile pass you get just 2 days of being able to use in own country, DE (can be many others as just DB, but not FLIX).

On the paper pass (can be bought on the spot at DB reisezenter too-discount is still there till 10/4) you have to write down the routing/trains used-and there have been some reports that your friendly DB-Zugbegeliter have sniffed at roundabout routings (like f.e.: you live in H, want to go to Swiss, but visit a friend in HH first=quite the other direction). And if you happen to hit a travelling special ticket-inspection team then you will have trouble in this case.