Background/Objectives: Hamstring muscle (HM) flexibility is frequently compromised in people with chronic low back pain (CLBP), contributing to disability and leading to a less favorable recovery. In a previous article, we presented the results of a study on the immediate effect of passive HM stretching on flexibility in 90 people with CLBP. There was considerable variability in the changes after stretching. The objective of this supplementary analysis was to compare the clinical characteristics of individuals who experienced a significant improvement in flexibility with those who did not. Methods: We fixed a threshold of 7 • to indicate an improvement in passive Straight Leg Raise (SLR) angle and differentiate between 'Responders' and 'Non-responders' regarding passive HM stretching. Results: Only body mass index differed between groups; it was significantly smaller in Responders (p = 0.007). The majority of Non-responders experienced workplace accidents, but this was of marginal difference compared to Responders (p = 0.056). Conclusions: Further studies should consider a broader clinical analysis with a larger sample size to understand which factors influence the HM stretching response in CLBP patients.