Accessing USB memory devices on S-series switches

Hi all - here is an easy question for you

I am in the process of configuring a mix of S12704, S6720 & S5720 switches for a client (and this is my first project with Huawei switches).

Previously I've been able to copy files to/from a USB memory stick when inserted in an AC6005, and I had assumed the same funtionality would be available on S-series switches. But that does not appear to be the case.

For example; on an S5720 running V200R011C10SPC600/SPH011, when I insert a FAT32 formatted USB memory stick I see the following on the console:

USBLOAD EVENT: U-DISK insert.

Sep 16 2019 09:46:11+02:00 DST S1-SM-P0C USBLOAD/4/UsbPlugIn:OID 1.3.6.1.4.1.2011.5.25.129.2.1.9 u-disk plug in. (EntityPhysicalIndex=67108873, BaseTrapSeverity=3, BaseTrapProbableCause=68073, BaseTrapEventType=5, EntPhysicalContainedIn=67108869, EntPhysicalName=MPU Board 0, RelativeResource=USB, ReasonDescription=USB plug in)

The USB disk is available.

But I am unable to access the USB device filesystem:

<S1-SM-P0C>dir usb:/

Error: Wrong device.

Similarly; I see no mount or unmount command in the CLI.

I confirm that USB-based deployment works on this switch using the same USB memory stick.

I've had a pretty good look through the documentation but I haven't found anything to enable the USB filesystem. Am I missing something, or is this functionality just not available on S-Series switches?

Thanks in advance.