The tool fails to remove the Lower Filters where relevant in the registry, causing the OS to fail to boot with Inaccessible Boot Device.
The original SPTD installer doubles as an uninstaller and can be used to safely remove them, if you can find a copy, the Secure-Duplex site has long been defunct so you might look at file mirrors for the original.
On Windows 11, all sptd drivers are already rendered unuseable by driver block listing, but this block does not render the system unbootable because there are checks in place for blocked filters preventing successful bootup, but there are no such checks in place for a Filter driver being removed entirely.