What I read(not from HK), was that the pin is the standard size, it uses a smaller push-pin inside the regular pin like on a Swiss Arms. That makes it look smaller.
As I said, I didn't get that from HK though, so I could be wrong.
My understanding is the barrels are being finished and rails supplied by Daniel Defense. The rest of the gun is HK GmbH and Wilcox.
Us getting European(I think Italian market) guns with the offset pins is the price to pay for getting things earlier than the USA, as well as State Department rules.
I'd be interested in a US market gun or just the upper for sure though.