IMO useful for temporary test installs or "portable" installs to USB 
devices.

The 0002-patch adds a related log message.


BTW: During testing I found that the "All Users" <> "Just Me" GUI 
setting has no effect at all. If setup is run elevated, "All Users" is 
always implied.

This is likely because read_mounts() is called again after the "Root" 
dialog. It resets root_scope and does not re-read the registry.

read_mounts (const std::string val)
{
...
   root_scope = (nt_sec.isRunAsAdmin ())? IDC_ROOT_SYSTEM : IDC_ROOT_USER;
...
}

-- 
Regards,
Christian