As in the title: the OS SSD, internal HDD and external USB 3.0 HDD are all shown correctly, but this ram disk (formatted to NTFS of course) is not, not even with -all.

This RAM disk is shown by the df command (I tried the one that came with git bash, the one that is in msys directory of Haskell Platform and the one in a Windows build of busybox, all three show it).