I can't pretend to know a huge amount about this myofascial release topic, only really what i've seen on the maker's Youtube videos, but I bought it after a massage therapist commented that my horse had tight hamstrings and tightness in her lumbar area, I use the tool on most days now whilst grooming, short sessions before riding during the week, and longer ones at the weekends, and it has made a big difference to the softness and 'jiggle' of my horse's muscles in a short space of time, and her range of motion on leg stretches has jumped up. I haven't taken pics yet to judge whether her actual posture has improved or not.
I think of it as a nice way to maintain the benefits of massage/physio inbetween sessions, and hopefully prevent small niggles becoming bigger impingements, and my horse seems to enjoy it as well.
Too soon to say what impact it will have long-term, but only positive, i'd imagine.
I'm currently doing some training but I did play around on my own horses previously
The Masterson method has a lot of YouTube videos and although it's not specifically myofascia the technique works well. There's some good books too. I also have a fascia tool but actually I think you need some training for those to avoid pressure on sensitive areas.