This was changed to be stretched in Patch 1.33 (August 17th, 2022). As far as I know, it is stretched for everyone.
You can try to drag that viewing area to be taller, but if you are like me then this solution is not very satisfying.
Edit:
I imagine a lot of Hive users might be starting to use older versions of the World Editor to work around this problem now.
For Reforged, since I knew from the Public Test Realm that all these things would become broken, I made a backup of my Patch 1.32 game and editor so that I can still use the old one that works better if I need to.