Bp. Sanborn checks people, not just priests, but potential Seminarians if not cradle trads, starting with their baptism. There’s lots of novus ordos that have invalid baptisms. Someone told me he doesn’t admit lay people to the Sacraments without first checking if they’re really Catholic starting with being sure they were baptized. If there’s any doubt at all, as in, they cannot prove a valid baptism by something like a video, sworn statements by reliable witnesses, he goes ahead and conditionally baptizes.
To me, that seems a little too excessive. After all, I can’t “prove” my baptism was valid. People didn’t have iPhones or easy access to recording video in 1960! I was conditionally Confirmed by +Bp. Williamson because my first time ‘round, it was plain strange, a V2 special liturgy written by and for the older candidates.