but it is what may be called a pious and probable belief among Catholics.
A "probable" belief? The more the RCC opens her mouth to explain her beliefs, the worse it gets for anyone who tries to make sense of this 2000-year-old-2-BILLION-plus group of "representatives" of Christ. But keep going. You have 2000 years of tradition to back up your claims...and lots of implicit scripture to decode for the 'faithful'.
Pelagius had a list of biblical personalities (including Mary) who were without sin. Enoch who rather than dying, was translated was included. Of course that got in the way of Augustine’s followers who thought that mankind was a lump of sin, so Pelagius was excommunicated.
As usual in such things, it was projection. Augustine was indeed a sinner, (”G-d make me pure, but not yet.”)who sold off his Roman citizenship as a tax dodge, while Pelagius was an inoffensive and austere monk.