Universal, the studio that distributed Cats, has thus far avoided official comment, and so we don’t really know if this is real or not.
One anonymous member of the VFX team has stated that, while there were never actually CGI buttholes, there were occasionally CGI shots that made it appear that there were CGI buttholes.
The whole thing started earlier this year when somebody claimed in a tweet that they knew a VFX technician who had gone through the movie Cats with the single job of removing CGI buttholes from the characters that had apparently been added previously.
But honestly, isn’t that basically the same thing?