Earlier quoted context omitted.
You have fallen into the confusing intersection between trademark and copyright. Files created by Facebook, depicting the trademarked Facebook logo, are copyrighted by Facebook. Files created by Feather, depicting the trademarked Facebook logo, are copyrighted by Feather. If the latter is freely licensed, with no restrictions on use, you may use that image in whatever manner you please. If you use it in a manner that…
What about the derivative works right? Although not a literal copy, one could argue that making one's own similar version of the logo could constitute a derivative work that could be construed as infringing.
But if you did do that, there would also be nothing transformative either, so your new image file would not be eligible for protection.
If it seems stupid and counterintuitive to separate the property interest in the file from the property interest in the image described by the file, that's because it is. But some people wanted to be able to have copyrighted digital image files based on artworks that have been in the public domain for centuries, so here we are.