Your comments

Okay, I was afraid that was the case.

But can I take this opportunity to suggest that this would be an AMAZING feature? Here's why:

- it would unlock the ability to use Textastic as the universal text editor on an iOS device. In any other app which had a text editor which I didn't want to use, because I didn't want the text to be locked in that app's silo, I could instead just put in a Texttastic URL to the text file in an external file provider

- this would enable workflows with better integration with the Mac, since on a Mac I can use a text editor of my choice to get at synced files on external file providers, and I will often prefer to do this than use, for instance, the text editor embedded in a Reminder's optional note.