It seems unusual that the government would post a list of domains that were obviously registered at a US based registry, and state that it's a federal offense for US companies to provide services to them.
On the big list of "unusual things done by the US government", this may rank somewhere down in the triple digits. I suspect the OFAC might possibly make an observation similar to yours in the future, which is why I believed the list might be useful to US registrars before such time. The domain for the "Islamic Army In Iraq" at iasite.net had entered expiration recently, and it appears that the domain name was subject to some interesting maneuvers after that. What is fascinating is that the name servers were restored, so the site continues to operate from its host - in Flushing, New York. One might compare that to, say, the Al-Aqsa Martyrs Brigade, whose registrar apparently allowed renewal of their domain kataebaqsa1.com, but has suspended their nameservers. The continued operation of such sites may reflect a decision to monitor, rather than to stop, such activities. If a US registrar does not have specific reason to believe that its dealings with SDN's are authorized, then it may be worth a run through the list. The relevant regulations and executive orders pretty much authorize the US government to haul away your entire operation with zero notice.