Questions....

While the replies are correct, the general advice is: NEVER export direct to a Flash drive. It is just not a reliable way of working because of how Flash drives are. Export to your hard drive in the usual way, then COPY to the Flash drive.

I really don't see the point of the two steps you are advising if you are using the export function of the organizer as designed. A two steps process has twice the chance to alter the file. The 'copy' stage may be considered as a 'backup' if you don't trust the result on the flash drive (or card), but it's much better to simply create an album (collection in LR) of your selection. You can reexport at will without creating useless duplicates. Deleting the album is faster and safer than deleting thousands of temporary files on your computer.

For me, the specific advice relative to PSE is: Don't use flash drives for the backup and restore process of the organizer. Use conventional USB drives for that backup. Not only because they are more reliable, but also because of some risks with the catalogs.

However, it's smart to use a flash drive (or a card) to transfer a large set of files from different dates which have already been processed and organized on another computer. The advantage is that the downloader has the option to create or recognize the YYYMMDD subfolders structure and imports directly in the correct subfolder.

However, using flash drives (or cards) to share files is practical; checking the result is advisable.