actually, it can work with some homebrew without any update.
It depends how the partition is initialized in the application.
This first sector (sector 0) contains the 4 primary partition informations (which format, which size, etc.) and the signature.
The stealth mode is done by modifying the first sector's last bytes (the MBR signature).
the partition information is still there, only the signature is different.
For example:
USBLoaderGX is checking the MBR signature before checking the partition list.
USBLoaderGX Forwarder is checking the partition list directly without checking if the first sector is really MBR format. (it expect the partition list to have the correct value)
The forwarder didn't require any update to see/mount the stealth'ed HDD, while the loader itself required an update to don't reject the modified signature.
Some homebrew could work the same way as the USBLoaderGX forwarder and don't check the signature, just try them.
I only tried WiiXplorer, and it doesn't see my HDD with UStealth activated