I've filed bug 3467 in SA's bugzilla
http://bugzilla.spamassassin.org/show_bug.cgi?id=3467
suggesting that uri_to_domain discount URI's which don't end in valid TLD's. There are test cases in which SA's get_uri_list can pick up URI of the form http://random.gif/ which will return random.gif as the domain and get fed into the pool of candidate domains to check for.
I don't know that SpamCopURI's behaviour is with the testcases I've filed
Regards, Yusuf