Exactly install FROM hdd to sd card. So you'd still not be able to play games on the usb but just install them on there to the sd card. It's discussed in the thread. The OP in this thread again asked about playing tiles from hdd. Obviously that is a huge difference.
I'm surprised you're spending time trying to correct me on something you're wrong about and not telling the OP to post in the n00b thread like you usually do.
oh and sxos is not able to install nsp to usb (from usb yes, to usb no), it load xci from usb, and thats something else entierly....
so at this point there is no way to load installed game from usb