I've changed my mind. This isn't a dual-outlet setup.
Looking down the throat of the mystery thermostat housing (I wonder what car that's from), it certainly appears that the hole in the head is blocked off. IOW, it should look dark back there if we were able to see through the housing and into the head. Looks more like the surface of a freeze plug. My bet is that he''s using that housing simply as a convenient place to anchor the hose from the back, and that it's got a thermostat in it.
I think this is his path:
So, basically, the primary coolant path is exactly like that of a traditional rear-thermostat reroute. However, I see a couple of crucial flaws in the design:
1: His heater core is obviously gone, as is the factory oil cooler. I see no water lines leaving the head apart from the big one at the back. What this means is that when the thermostat is closed, there's going to be absolutely zero coolant flow through the head. None. Nada. Total stasis.
2: For some reason, he's taken the coolant outlet at the rear-exhaust side of the block (which would normally feed the turbo) and is looping this back into the mixing manifold. I assume he's done this so that there will be coolant circulation through the block when the thermostat is closed. There will be a tiny
amount, however still nothing going on inside the head.
3: If the thermostat is indeed up inside the front housing, it's going to take half of eternity for it to open. IOW, there's a lot of stagnant coolant sitting in that long hose between it and the back of the head, so the thermostat isn't going to be exposed to what's actually going on inside the head.
I predict eventual failure due to cracking or warpage of the head, and possible damage of the exhaust valves. I'm strongly disinclined to say anything about it to him, as I really want to see him destroy yet another engine.