The US does not give a damn about PKK. They used the Kurdish sister organizations in Syria and Iran. They condemn PKK because Erdogan wants it.
The US would have zero issues with a Kurdish state comprising parts of Turkey and Iran that splinters the region even more.
In this context, "designated foreign terrorist organizations" is not an explanation, but a tautology. The matter at hand is how and why something got onto that list.
The antifa remark relates to the Rote Hilfe situation. In my opinion, it's an example of how populist rhetoric became a major overreach with real consequences prior to the incident at hand. Rote Hilfe had a very weak relation to "Antifa Ost" (hardly worth US attention). That's how they got cancelled: https://www.state.gov/releases/office-of-the-spokesperson/20...
So the antifa moral panic is indeed very much relevant.
But decide for yourself, if "Antifa Ost" deserves US anti-terrorism attention to the extent of OFAC sanctions, or if it's maaaybe populist action... https://en.wikipedia.org/wiki/Dresden_left-wing_extremism_tr...
Incidentally, funny how the NSU isn't on that list, hm?