Because, as I said, it was more of a by-product of his height and the length the team needed him to bowl. I don't think Anderson should be ranked lower than Walsh because he is 3-4 inches shorter. And one is an into-the-deck bowler, and one is a swing bowler. Anderson could've operated short of a length his whole career, gone for a few less runs an over (especially on flat days) and been half the bowler he is. The by-product of him being a world class swing bowler was going for slightly more an over than Walsh. I don't believe that should cost him one iota in terms of a career comparison.
There seemed to be a decent consensus that Walsh>Anderson and I just don't think that stands up in any sense. Both did the job to a world class level. Walsh averaged slightly less and was consistent across his career. Anderson started slowly but was every inch world class in the last 10 years of his career, even away from home. Anderson was born in England, to become a slightly above average height, and played half his cricket in English conditions with a Dukes ball. And given those unique circumstances, he became the best bowler he could be and that his country needed him to be. I don't get the 'he was rubbish in Australia, couldn't bowl with a Kooka etc' which for a start isn't the whole truth, and in any case is only part of the whole picture. He won as many Tests for his country as he could by bowling the way he did in the conditions he was given.
To me he's an ATG. 452 wickets across a decade (2010s) at 24 nicely secures that for me. But to others, he isn't. Each to their own.