While many Aikido techniques do favor "with the joint" movement, not all of them do. Quite a few Aikido techniques go against the joint (hijijime (elbow lock/throw), sankyo (arm twisted), reverse sankyo (arm straight), and a few of the kansetsu (pins)).
Most of Segal's movie techniques are Aikido (except the odd kick or punch, which are assumingly goju-ryu Karate (really atemi is atemi though)).
His parrying/opening movements are all based on the movements of the Aiki-ken -- check out some of his teachers (such as Seiseki Abe) and you'll notice quit a bit of familiarity.
Certainly they were all categorized as Jujutsu originally (Daito-ryu Jujutsu I'll even wager
), but they are Aikido now!