RISCOSpi Filer missing when booting from USB

The Pi3 (possibly others) can boot from USB without an SD card, so I wrote the current SD image to a USB drive and booted from it. The default CMOS of the Pi SD image is set to SDFS, so a few commands are needed to correct that:

SCSI
DIR !Boot.Loader
Configure FileSystem SCSI
SAVECMOS CMOS

After a reboot, it boots correctly to the desktop but the Filer icon for RISCOSpi is missing and replaced with a filer for PiBoot (Fat32fs::PiBoot)

If you drop to the Supervisor, the CSD is SCSI::RISCOSpi.$ so what am I doing wrong?

I think this is Fat32FS being Fat32FS.

Try right-clicking on the drive icon. You may need to dismount the drive first.

That is indeed the issue.

Now I’m left wondering why SDFS doesn’t behave the same!