Used to be allowed but things changed. Just going off the top of my head here but iirc
What happened often times is that judo competitors would grab the legs, get a minor score, and then be defensive once they achieved that score. A lot of the matches were bow, fight for grip, dive for the legs, hope for a low score, and then be defensive for the rest of the match doing just enough to not get called for a shido. It was rare to see a single leg or a double leg score for ippon but back then it didn't matter. The players were coached to fight a certain way because the ippon doesn't matter. Winning does. So they cut that shit out like a cancer