BUG?: Lightroom Classic CC appears to use the wrong XMP keywords on initial upload to Lightroom CC

As described in this thread https://feedback.photoshop.com/photoshop_family/topics/lightroom-classic-cc-keyword-hierarchies-not-... , it appears that Lightroom Classic CC is writing keywords that Lightroom CC is able to display after initial upload using the "lr:hierarchicalSubject" section of the XMP sidecar rather than the flattened "dc:subject" section. While this maintains the keyword hierarchy that Lightroom CC doesn't otherwise support, it leaves the keywords in ugly strings (top_level|sub1|sub2|sub3) rather than a set of separate keywords. This seems odd, since Lightroom CC does away with hierarchical keywords entirely, so why read from the XMP section that explicitly applies to keyword hierarchies?

This change seems to have happened over a year ago, but I didn't notice it because I was only using Lightroom CC for certain parts of my workflow where keywords weren't ever a consideration, and the large bulk of my library wasn't uploaded. It may relate to the change from Lightroom CC 6.x to 7.x - that's when the switch happens in the files I've looked at.