But why does Korindo call itself "Aikido", if it does not refer to one of the Aikido sensei?
The term aikido was first used as a general category for a grouping of martial arts. Basically I believe it pointed toward arts that were not competitively oriented, and had links to koryu, though they were practiced as modern arts. In a general sense of course, and with all the usual caveats. Aikido Journal has some good articles on how the name was given.
The founder of Korindo aikido did train for a time with Ueshiba Sensei, but apparently he considered himself a contemporary more than a student.