Thanks for you question. We don’t often get to talk about the sacroiliac joint (SIJ), and of course, like all joints, it can be subjected to too much stress. I have not read the article by Judith you are citing, but I have read other thoughts by her on this topic. I believe her main concern is not making a somewhat damaged or tweaky SIJ worse, and thus she recommends twists should occur higher up the spinal column and not at the SIJ itself. This can be good therapeutic advice for many people.
However, the SIJ is designed to allow some movement for most people (but not every body!) A healthy, undamaged SIJ should accommodate stresses that move the pelvis independently of the sacrum. In most seated twists the pelvis is fixed to the ground (the sitting bones rooted) and the twist comes from the upper body. This can cause stress at the SIJ and in the associated fascia wrapping the area. There is nothing the matter with that: that is normal anatomical movement. Simply walking places stress in the SIJ. But, if the area is damaged, it may be wiser to restrict movement there. A reclining twist may be safer for someone with SIJ instability or damage. In the reclining twists the pelvis is free to move with the sacrum and lower spine.
Like all joints, the SIJ needs some stress to remaining optimally healthy. The trick is to find the Goldilocks’ position
where the stress is not too much nor too little. Beware of alignment cues that avoid all stress on any joint simply because we could do too much there. Yes, we could do too much anywhere, but if we do nothing, we risk, making that joint ”fragile”
. If the area is damaged, then obviously greater care must be taken, but perhaps avoiding all stress is not the healthiest option even then.