Everything here runs under consent and the ability to pause or stop — either of you, at any time, and "holding on" is never an obligation. In this position, plan for stopping as a sequence: movement stops first, then untangle, then talk.
Being held from behind isn't comfortable or wanted for everyone — if being wrapped up feels confining, triggering, or just not appealing, not using this position needs no reason. And some situations have no direct research to lean on: pregnancy, postpartum, joint replacement, chronic shoulder or hip injury, larger bodies, disability, trauma history, or sensory sensitivity. If any of those are yours, someone who knows your situation beats a generic list — after spine surgery even reviews find the position evidence inconclusive (Malik et al., 2018), and for hip arthritis, pain and stiffness are the main sexual complaints while surgeon guidance often stays generic (Issa et al., 2017).
For low back pain, see the conditional picture in the steps above — which end of the recommendation side-lying falls on depends on which partner and which movement intolerance, so match it to your own situation rather than the folklore. And if discomfort you've flagged keeps getting ignored, that's a consent and relationship concern, not a positioning one.