This is very cool. I had a very similar idea, although I was probably inspired by the same UX you've seen elsewhere.

I had already built an index cards app for Mac and iOS and it works really well for what it does, but the fixed size of the cards always bothered me since you're always limited vertically by the card, so I wanted to try a horizontally scrolling note editor like you have here.

I put together a quick prototype of the idea I came up last year. Here's a recording I did just now: https://www.youtube.com/watch?v=6V-kCD2aXcQ

Also inspired by Andy Matuschak's page. I've been meaning to work on it a bit more and get in the app store but have been busy with other projects.