It could also be that the 160-degree stat was "pinched" in when in the housing by not being centered when the stat housing was bolted down, causing it to bind. It could also be the fact that SOME engines (as mentioned earlier in the thread) develop strange water flow patterns that create eddies and dead spots when the water flow is too fast through the block, leading to overheating.
But the one thing that is physically impossible is for it to be that the water "moves too fast to cool off" in the radiator. Yeh canna change th' laws o' physics.