Korosan Group was targeted because they had direct information where the leadership was located......these were people also tied to 9/11....the leader was photographed next to Osma- ben-ladan after 9/11
The leaders is known to recruit and train members to strike US .
Khorasan is the old Arabic name for the Afghanistan/Pakistan area. I wonder if they are from there, or as you mention, represent a link back to HQ in the Khorasan.
I saw another report that they were selecting Westerners from among those who came to support ISIS, and were screening/preparing them for attacks in the West. I would assume that al Queada HQ would need to have some folks in Syria for just that kind of function.