Interesting. It was my impression that Donald Rubin was the main instigator of propensity-score methods. Do you have some paper references in mind to give me a better sense of the timeline?
Quite possible -- Robins was pointed out to me as one of the pioneers by Sander Greenland, around 2008 or so? I'm more of an experimental/clinical statistician at this point. The work I did with propensity scoring and doubly robust estimation convinced me that shrinkage was a less-bad approach for the things I needed to do. YMMV.