I have never heard such a thing. I have been a practicing Roman Catholic all my life and I never heard that. It is sad. I was taught those free from sin are welcomed into Heaven.
Well, of course, there always the arguments that 'you gotta be Catholic' or 'you gotta be born again' to get into heaven. The WELS teachings are that the WELS churches are not the only saving church. As it is, I respect ANYONE of faith. It is very difficult in this world to stay in Christ.