Well, I think the massages helped with mobility when it was quite bad (at times bending forward/downward didn't just hurt, I just couldn't do such movement), so they might have relieved tightness, and they had a firm pressure that kind of hurt as pressure, but I don't recognize any sensation I'd describe as "unknotting", like that sequence where it hurts worst in a specific spot and then relaxes is not something I recognize.

Some of the back pain books I've read described this technique as well with a small ball or as self massage for pain relief (not with a foam roller though, hence my confusiom) and described which areas to try for these "triggers", and I tried that for alleviating the pain -- my sciatic pain at its worst was the worst pain I ever felt, worse than an abscessed tooth, was constant regardless of sitting/standing/lying and oral pain meds didn't do anything, so that were some really unpleasant weeks and I was game to try all sorts of stuff from temperature to pressing on various body parts to positioning my back and legs or whatever to make any sort of difference -- but I never found any spots that produced this kind of effect.