> Neither do the other apps I mentioned.
Not true. I don't know about nvalt, but Notational Velocity Bear and Ulysses are all saving things in a local database and sync them to the cloud. And all have their own special view on the data too. There is no direct filesystem-access.
> They are not general purpose editors meant to just open whatever random file
I was talking about folders, not files. And not just any random file or folder, but obviously folders with files supported by Obsidian. Which BTW is also not limited to Markdown, thanks to the plugin-system.
And Obsidian is even supporting this, but only through the clunky Interface.