You know better than to say “it works both ways.”
Catholics who are baptized Catholics will Alwyas be Catholics, even if they choose to be inactive. They are always welcome back.
Many share their stories about coming back at this site: http://www.chnetwork.org/
I will say again...catholics leave the church as much as those who enter...it works both ways...now the catholic church might think once a catholic always a catholic....the Mormons say the same thing as do other faiths...that does not make it so. It does work both ways and you should know better than to say it doesn’t.
Better to say one is Christian...believes in Christ and follows Him.