Great solution, up until more than one person clicks on Export and one of them gets an error or one gets the wrong export.  I would code in the actual path to the file using the site/library/file instead of the SharePoint generated GUID filled URL, and stamp something unique into the name per Export click so that multiple files are being created (multi-user compatible), and then also follow up with some cleanup deletion of the temporary file.

 

This aside, the whole PowerApps infrastructure, how you need to throw files in temporary locations between 3 or 4 different cloud solutions while paying subscription fees to someone to have access to a premium connector to do all of this is just so hacky and inefficient.  If I were coding this in an actual website with actual code, there would be no temporary hacky anything.  Click export, generate CSV in memory, throw the byte[] array and appropriate content-type at the browser, done.