When I first watched a video with Pattabhi Jois leading a Primary practice, I was surprised that parivrtta parsvakonasana was omitted. I thought he forgot at first but after researching it I found that he considered it a “crazy posture!” and it was not included in the sequence at first.
Revolved side angle is not an easy posture, but it can be modified with hands in prayer instead of split, with the back foot in a lunge position instead of grounded and angled, or with the back knee on the mat for additional stability. If you have back issues keep the torso square to the floor and lengthen your spine instead of rotating. If pregnant, either do not rotate, just lengthen, or rotate to the opposite side for an open twist with room for your bump (extended side angle).