I confess that this is the first time that I have come across this study design. I asked questions about how they would compare this type of study to a prospective cohort, what they thought about the lack of control groups, what they thought about the randomization - or lack there of - etc.  Mostly I heard that they loved this study design because it is "real." They seemed to value this design over an RCT because it draws from patients with comorbidities and who self-select a treatment arm, as opposed to RCTs that are careful to eliminate comorbidities and use proper randomization.