Being more active in general (walking or running) should alleviate some back pain. Stretching alone wouldn't and shouldn't be expected to because the problem isn't "my muscles need to stretch" it's "my muscles need to be in use" and they need to be in use in a full-body context, not in isolation.

Glad to see you've found something that has helped with your back pain. I've been taking more walks now that my life has gotten a little less chaotic and the weather is warmer and what do you know? There goes the back pain. Standing desk helps too but it's mostly the walking.