A few practical adjustments to sleep position and setup are commonly recommended for lower back pain, independent of any specific stretching routine.
Side sleeping with support
Sleeping on your side with a pillow between the knees keeps the hips, pelvis, and spine in better alignment, reducing the twisting strain that can happen when the top leg drops forward unsupported.
Back sleeping with knee support
For back sleepers, a pillow under the knees reduces the natural arch of the lower spine, easing pressure that flat-on-the-back sleeping can otherwise place on the lumbar region.
Avoiding stomach sleeping
Stomach sleeping is the position most commonly flagged as unfavorable for lower back pain, since it typically increases lumbar arch and can also strain the neck from the head-turned position it requires.
Is it worth changing a long-standing sleep position habit?
If the current habit correlates with worse pain, it's worth experimenting — sleep position changes take some adjustment period, but many people find a noticeable difference within a couple of weeks of consistent practice.