It's possible that he has had other bypass patients report that cheeses, etc. did not give them issues. I know someone who still drinks milk post-bypass, so I think problems/severity is variable.
If the cheese is properly aged (which almost no cheese is these days) then it should contain no lactose. But that takes years. It's just like dry wine - given the proper conditions and the right starting ingredients, fermentation should continue until all sugars have been consumed.