(In case it helps anyone else, "unpartitioned" here means "just one partition". I got confused at first thinking the drives had no partition at all, until I saw they were all NTFS in one of the screenshots.)
I'm not really sure why this would happen, although the tree and file display do get the names via somewhat different routes. What's strange is that the tree's route is more similar to what Explorer would use, but it's the one that is different to Explorer.
What happens if you fully exit Opus and then re-launch it? Does the tree get the correct labels then?
Also, try turning off Preferences / Folders / Virtual Folders / Native display of 'Computer' and see what the file display (right pane) shows then. That will be using Explorer to populate the Computer file display in Opus, so it will be interesting to see if that matches what Explorer itself displays or what the tree displays.