@Underexposed: If I load pphoto’s xmp it looks exactly like his post.
I’m on darktable 3.3.0+1729~gc81f80f3d and use Debian (10/buster).
Many, many PR’s have been merged the last few weeks, features and changes alike. This due to the 15 November feature freeze. Which in turn is now in place for the X-Mas 3.4 release transition.
So it might just be possible that your development version is “out-of-date”.
Beyond my skill level in RT 5.8 to mask only the blue berries, the shadow of them has a green tint so the mask misses in the current colour toning module, though in RT 5.9 I believe there are better masking/ selection tools.