I’m not especially familiar with the history of MBSR. What I know more is that when I’ve seen self-described mindfulness practices presented they often rely more heavily on techniques I would associate with vipassana. Also you’re correct that Thien is the Vietnamese lineage of Chan Buddhism (Zen is the Japanese lineage of Chan, Keown is the Korean lineage, and Chan itself being the Chinese version started when Buddhism was brought to China), although each one is divergent enough in the specifics that it’s hard to say they are on-the-ground similar other than pulling from a common set of historical texts and practices. Given the high prevalence of Theravadic practice in south-east Asia, though, it doesn’t seem all that surprising to me that Thien practices might look a lot like the neighboring practices and maybe that’s what I’ve noticed.
I’m not especially familiar with the history of MBSR. What I know more is that when I’ve seen self-described mindfulness practices presented they often rely more heavily on techniques I would associate with vipassana. Also you’re correct that Thien is the Vietnamese lineage of Chan Buddhism (Zen is the Japanese lineage of Chan, Keown is the Korean lineage, and Chan itself being the Chinese version started when Buddhism was brought to China), although each one is divergent enough in the specifics that it’s hard to say they are on-the-ground similar other than pulling from a common set of historical texts and practices. Given the high prevalence of Theravadic practice in south-east Asia, though, it doesn’t seem all that surprising to me that Thien practices might look a lot like the neighboring practices and maybe that’s what I’ve noticed.