Yeah obviously the principle is the same !! lol, what they have done though ......... ready for the magic ? Is ram every available space thats left open in the normal imac full of heatsink fins, then added 2 fans left and right pushing air sucked in from the bottom, one of the CPU and one of the GPU, then both fans eject air through the 3x3 inch gap at the back where the ram door used to be.
Now - I'm not an apple fan boy, but I have been custom building and cooling PC's for over 25 years - I've done it all, large air cooled, large water cooled custom builds - I even use a car radiator once !! haha
Anyway essentially imagine a large heatsink, thick in the middle, thin on the outer edges (which is ideal for thermodynamics as the outer edges are less densely packed) - about 80-90% the area of a 27" monitor ?????
There you have it a (comparatively) enormous heat sink for a desktop machine - the key is they have been ever shrinking the systems motherboard and hard drive physical sizes ----------
This has allowed them to pack a 14nm 18 core + vega into an imac chassis.
The mainboard + hard drives is barely larger than 2 mobile phones in area.......of course by far the biggest room taken up by the cpu socket (probably soldered on, not sure however - I don't think intel would allow that on a workstation class chip)
And id guess the GPU is on a daughter board to allow the left / right fan flow setup of the design.
Anyways I'm sure and im hoping a rich you tuber will take it apart very soon and we can see.
However based on physics, a heatsink that size in area (probably dense fin spacing also for more surface area),
I'm standing by my prediction it will run to spec For all my reasons and theories stated.