ZLL defaults to ZHA when joined to a ZHA coordinator.
But if the device requires touchlink commissioning, it can’t necessarily be joined to a ZHA coordinator. This comes up with quite a few devices designed to integrate with the Hue bridge.
Also, the new zigbee 3.0 standard does not require that devices have an alternative join method to touchlink commissioning.
And a zigbee 3.0 coordinator is not required to support Touchlink.