I'm not sure I totally understand whats going on here, but it seems he has created a bumbike fixed gear thread on hub from a a weird old freehub? He is using a bottom bracket lockring to hold on the cog so theres a chance it could unthread unless I'm mistaken.

To the OP. Just use spacers and run the bike SS until you are ready to buy a fixed wheel. Nobody will make fun of you and you won't destroy a hub in the process.