it looks like 3 layer single pass. The guy boasts that his invention has very low flow resistance to the liquid..... a plus if your blocks are less restrictive than your radiator, I guess..... I don't have that problem though
Problem is, he is but merely running 3 single layer radiators, on top of one another, hooked up in parallel. the first layer does all the work, and the other two beneath it is all nice and toasty in the hot air from the first. A very good compromise, to gain compactness, If you are cooling a 700Kw+ 20b Rotary engine that has on exhaust manifold temperature of approximately 956ºC, give or take....
an unmodded heater core is a 2 pass single layer, all be it a 2" thick layer. if one modifies the core's tanks, to have an inlet on either side, it would be even better.
on closer examination of what he is saying.... hmmm, I'm starting to lose the awe I acquired from just looking at his creation.