Interestingly, if the dock with the two monitors (at work) is connected via Thunderbolt, the naming of the interfaces is different (DP-5 and DP-4 instead of DP-1-2 and DP1-3 with the L390). This can be seen in the old monitors.xml from the first post (where it was connected to a L390 via USB alternate mode DP) and the monitors.xml attached here, which is created on the T470 with a Thunderbolt USB-C alternate mode.
monitors.xml
Description: XML document
