Tom , you've performed a random action, of writing the Media Creation Tool direct onto the target USB stick and it's randomly worked for some people. You could have just as well have thrown holy water over the USB stick and it might have worked.
From https://www.diffen.com/difference/FAT32\_vs\_NTFS
"All operating systems support FAT32 because it is a simple file system and has been around for a really long time. NTFS is more robust and effective than FAT since it makes use of advanced data structures to improve reliability, disk space utilization and overall performance. Support for NTFS has grown but is not as universal as FAT32."
So maybe formatting the USB disk in NTFS might pick up on any errors writing to the disk or correct any errors after being written to disk.