Also the seiyuu seem to influence ships as from what I remember Aikyan (Yoshiko's VA) and Rikyako (Riko's VA) used the nickname Lily (Riko) and Yocchan (Yoshiko).
That and Uni (and her older sister Noire) and tsunderes for Nepgear (or Neptune in Noire's case). The games also help support this ship especially with Uni's optional voice in mk2. "I love you Nepgear!".
Maybe the person who uploaded the image didn't know that Lady Bat was a guy? There's also the possibility that Lady Bat was genderbent in this image and is in fact a girl and not a crossdressing guy- in which case the yuri tag would apply.
If anything this manga seems to be a more realistic take on the harem genre in anime. In that indecisiveness ends up making all people in the relationship unhappy.