I haven't done an exhaustive test but so far my observations are:
Single file erase works with file extension .exe, .tif, .jpg
but single file erase does not work with files ending with extensions .rtf, .com, .txt, .htm, .pdf, .txt, .ini.
What happens is it just removes the archive attribute but does not erase the file.
However, as long as I select more than one file - it doesn't matter what extension they are, the erase works.