There is a possibility to find out if these “scaps” are images of a file system or not. In Linux and also in macOS a file can be mounted just as it would be a partition:
mount -o loop <filename> /mnt
This command will try to determine the filesystem used by filename image and mount it into /mnt folder. You can also suggest its filesystem (expected fat32) by passing the option -t fat32. Linux also knows how to mount HFS+ (I don’t know if APFS also works).
Another option is to try to open such a file with some archiver application. They are known to “open” *.iso files and you can see and extract their contents.
Finally (but actually this would be the first action to try), you can guess whether the file contains a filesystem by compressing it. Usually flash images’ sizes match to partition size, but their content takes much less space. So these images contain a portion of meaningful information followed by zeros (or garbage). If the size of compressed file is much less then the size of uncompressed file, this usually is a good indication of a flash image contained in this file.