All things Palo Alto Networks
Is the mgmt interfaced used for updates, licensing and so on or does it just depend on routing?
The management interface is used for all management related connections by default. The default route configured in device > settings > interfaces us used as next hop for everything the management server needs to do (dynamic updates, cloud lookups, licenses, dns,...)
Only if you create a service route in device > setup > services can dataplane interfaces be assigned to handle specific connections. Connections "attached" to a dataplane interface via sercice route will start following the Virtual Router routes