>>12430805The four things a pair of women can do (licking, gropig, kissing, rubbing) can also be done by a pair of men, but the one thing a pair of men can do that a pair of women can't is penetration using a real human genital.
If you consider sex solely for the purpose of pleasure to be forbidden, it would make sense to also forbid any kind of carnal pleasure activities between a pair or more of women.