But, see, I feel this depends a lot on the resolution of the admixture graph you're using (which probably reflects the main purpose of the graph in the first place). If you make a, say, K=6 graph using very divergent modern populations, like West Eurasians, East Asians and South Asians, you could mistakenly believe that Spaniards, Russians and Lebanese are very similar. That's why I always interpret these K= admixture graphs very cautiously especially if they'e comparing very divergent ancient populations like ANF and WHG vs. CHG and Iran_N.
That said, as I commented in my earlier post, I think CHG and Iran_N are close enough that they're best seen by most geneticists, particularly in comparison with other genetic structures that later admixed increasingly, as two ends of a shared genetic cline, not as totally distinct populations that can be very easily distinguished.
They're distinguishable on a PCA and do not overlap, and CHG apparently (IIRC) had some EHG-related ancestry while Iran_N had more Basal Eurasian. But that could be just a part of a wide cline from the Caucasus to the Zagros to the Eastern Plateau of Iran (I say that because the recent South Asian paper claims that eastern Iran_N and western Iran_N had diverged much earlier than previously thought, some 10,000 years ago). Since geneticists can't pinpoint where precisely in that cline a given Iranian and Caucasian-related population lived to contribute later to the admixture makeup of a given population, sometimes they think distinguishing both is not worth the effort and they are better understood as more or less the same thing. I doubt all CHG were 100% Satsurblia-like, and for Iran_N we can for ourselves conclude they had some internal genetic structure, because they do not overlap very tightly.
I'm still unable to post my pictures here, I don't know why, but see in Imgur what I mean:
https://imgur.com/a/CNkUf5A. The most distant Iran_N samples are not much less different from CHG than the closest Natufian and Anatolia_N individuals. So, certainly very similar, but not exactly indistinguishable. I don't think we disagree about that.