Hello, after checking with the Devs this was an intentional change for this cycle. The benefit of a FMF filetype is that we can ensure the file has been saved in the PGE and therefore will not falsely appeared as verified in game as can be the case with user edited XML files.
However, our working assumption has been that, with the ability to import/export XML files within the PGE, users can just import any XML file into the PGE, save as a FMF filetype, and otherwise function in the same way as before. We would need to check if there's any drawback to this method.