even Catholic scholars admit that there is no evidence for Peter's mythical sojourn to Rome.THAT's the part that's untrue--the "even Catholic scholars" bit. The very Catholic scholars you quoted said that we possess no precise DETAILS of the sojourn, but the evidence is indisputable that he was there.
Here is a very good and detailed link from New Advent
http://www.newadvent.org/cathen/11744a.htm#IV