I'm sure you're aware of https://www.sleepio.com (I followed their program a few years back). They use the same (similar?) CBT approach and I do think it helped but was far from a silver bullet.
Does Stellar Sleep delve into sleep hygiene? Are "edge cases" considered e.g. some people report no difference with cutting caffeine (as mentioned) but others cut caffeine and instantly their insomnia is cured and their lives change.