Apparently Google Drive handles some files differently. They appear to be created by google apps such as docs, slides, etc. If you download them via drive.google.com, google seems to decide on the fly to give them a format. Otherwise they appear in a ftp listing as having zero size.
I know it is possible to deal with this. For example, multcloud.com file explorer can deal with them by asking at the time, what format do you want. But not sure how they deal with downloading a directory with several of these files.