Kind of. To my understanding, it proves that there was some sort of proto-Indo-European speaking people (as Reich calls them, the pre-proto Indo Europeans) in Armenia/western Iran. According to Reich, the Proto-Anatolians moved westward from there (I seem to recall reading somewhere that it's thought that the Proto-Anatolians might have been around Lake Van before moving westward, but I'm not sure why the reason for this is), and the rest moved northward and mixed with EEHG to become the Yamnaya, who then split and became all non-Anatolian Indo-Europeans.
I have a few issues with this, however. A) Arguably, this does prove that Armenia/Iran is the Indo-European homeland, and really, shouldn't Reich's Pre-Proto-Indo Europeans be called Proto-Indo-Europeans? The "pre-proto" part bothers me, especially because it's still commonly held that the Anatolians (Hittites, Luwians, etc) were Indo-Europeans, just a branch that split off very early. B) While they've found some skeletons in Armenia from the Middle/Late Bronze Age with European Steppe ancestry (which suggests that the people were Yamnaya-derived) there's 1) no reason to assume that these people were Armenian-speakers and not another group, such as Cimmerians and 2) there's a lack of Steppe-derived ancestry in your modern Armenian, which means that whoever these Steppe people were, if they were the ones to introduce the Armenian language to the region, they were either a very, very small group or somehow introduced their language without mixing with the native populations (who modern Armenians are descended from) and then died off/disappeared/migrated elsewhere. If they migrated elsewhere, you would assume that there would be an Armenian language or Armenian names appearing somewhere else than NE Turkey/modern Armenia. The only thing I can think of is perhaps these people moved slightly west to Cappodocia or SE Anatolia because there are some ancient names there that could potentially be of Armenian origin, such as Mount Erciyes (Mt. Argeus/Harkasos), Haria, Melia, Togarma, Armatanna, Aravanna, etc. But some/all of these names could also be from Anatolian IE or from some other IE language.
I just don't understand why we still call the Yamnaya the Proto-Indo Europeans and the European Pontics the Urhemeit, when clearly it had a preceding culture. Seems like it's kind of moving the goalposts a bit. In the case of Armenians and Iranians, it makes more sense to me that they just stayed in the same general region than went all the way around the Black and Caspian Seas, respectively. And as I said, I know that modern-Armenians are more similar to EBA samples that they've found in Armenia than they are to some MLBA samples, which have Steppe ancestry. I don't know much about Iranian genetics though.
Do you have any thoughts on Sergent's Zagros theory?