According to "Best Aikido" by Ueshiba Kisshomaru, Nikkyo and Sankyo et al are just variations of Ikkyo. That picture looks just like movement in the kihon Nikkyo omote that I was taught when I lived in Japan, although I think it's very much the end pin that really differentiates Ikkyo and Nikkyo. That pic could still end up with an ikkyo pin without using the wrist, equally at that frame in the movement it could be Gokkyo. Here in the west I've seen many people use the twist on the wrist there and call it Ikkyo, their Nikkyo is then done "differently". What they effectively do is the ura version of Nikkyo whereby they enter into an omote movement but they manouvre the arm into the "S" shape and bring the wrist into the shoulder to apply the pin.
There are numerous variations on the kihon versions of both omote and ura, so it's highly likely that different people will be taught "different" kihon waza.