P&W R2180-E What's the deal?

I understand the R2180-E is a somewhat unique design among radial engines. I have read on one hand that it is just half of the corncob R4360 and I have also read that it isn't. That it would have existed no matter if the R4360 was made or not and that there were significant differences.

Can anyone clear this up for me? What made this engine unique, better than other radial designs?

I wish there was a book devoted to this engine. I have one on the R4360 and it has a blurb about the R2180-E being similar but different.

Stating that R-2180E was half of the R-4360 is probably simplification of matters? The rows will be stacked in different way, with second row rotated exactly by 1/14th of the circle vs. 1st row. That means a brand new crankcase and crankshaft. It will certainly feature a new supercharger, new valve gear, new way the baffles are designed, new air plumbing between difuser and cylinders, new reduction gear (that can be lighter due to lower loadings) etc. New ignition system. Probably a different vibration pattern?

It was unique all right, but not enough to make a lot of difference. There was no superchaging worth talking about from military point of view, and with developed R-2800, R-2600, Hercules making the post-war glut, the commercial success was modest. I don't think that we can say it was better than those established engines.

FWIW, the fact sheet for both the -A (pre-war Twin Hornet) and the -E engines (post-war Twin wasp):