Side bending, aka lateral flexion, done from an inverted position challenges the stability of the foundation. Keeping the head on the ground can help immensely, but the shoulders and their associated muscles reap a lot of benefit because they have to keep the weight anchored. This is in some ways easier in lotus because of its compact nature... and in some ways harder, because finding true hip extension as opposed to lumbar extension isn’t so easy... give this a try and tell me how it goes.