tl;dr: Hype always keeps its own copies of files and “Edit In…” works on those. To use external editors, a temporary copy is made which is only known about for as long as the Hype document is open.
There’s a bit of history and coming up platform limitations Apple has imposed, so I will try to clarify.
Hype has taken the approach of “preserve a working document at all costs” which means that when an asset is added to a Hype document, it is copied into that document.
If you were to change the dimensions of the original file, modify it in ways not for a specific document, or trash it, we would not want to modify the Hype document. While there’s a lot of workflows where this is desired and intentional, I can tell you there’s a lot where it isn’t and we’d get tons of support about broken documents!
Therefore your Hype document is insulated from any changes of the original asset and you can move around the document to different folks or different computers and have everything operate without missing files.
We do try to preserve a link to the original file so you can edit that and hopefully Hype will pick up the changes.
Unfortunately the App Sandbox feature makes it ridiculously hard to keep track of these files correctly in most cases (see my above post). Pretty much if we want to be on the app store, we cannot count on being able to see any files outside of the .hype document.
So given that we have our own copy, and we might not be able to see the original, the “Edit In…” features acts on Hype’s copy.
If you close the hype document, it then loses the connection to this scratch file. So you could keep making edits, but it was really only meant to be a temporary proxy for what is currently in the Hype document.
Is this the most ideal workflow? Probably not, but it gets around some larger issues and deals with platform limitations. There’s definitely ways it could still be improved and clarified.