Catenate means to connect things together[1], which implies it was named with multiple files in mind.
https://en.wikipedia.org/wiki/Cat_(Unix)#History
Whereas "con"catenate means to link separate things together. These are minor distinctions, but if somebody is going to call things "asinine" they should at least get the pedantry correct.
Edit: that wikipedia page makes it sound like the program it replaced was the one that prints a single file to the screen.
How’s that for pedantry?