The riding tag is normally used when someone is riding an animal or a small vehicle, like a bicycle or a motorcycle. However, the tag is misused by several users who think the tag also applies for cowgirl position and reverse cowgirl position.
I would propose something like tied up (nonsexual) by having the tag being renamed to riding (nonsexual), and the current tag would be deprecated to prevent another mistagging to ever happen again. If there is any objections, feel free to post any before I could propose the BUR.