Thanks for capturing this. Indeed, Licat and I have been chatting about this for a week or so. It has been a nuisance to solve!
I think this is a bug caused by how Obsidian’s declaring what file types are compatible with its iCloud Drive app library (i.e., the Obsidian folder in iCloud Drive).
The bug also has other effects: you can’t save items into the vault from other apps, either, for example. So, if you are in a Word doc and you want to save it to an iCloud Drive vault, you have to save it to e.g., the desktop then copy and paste.
You see similar behavior if you try to save incompatible files into other iCloud Drive app libraries. For instance, try saving a .jpeg into the Numbers app library.
If anyone out there has experience with app development on iCloud Drive and
CFBundleTypes, reach out!