I think the idea is to implement it now, not to change the records. Changing it now would make things asymmetrical (not the same kind of stat as before) it is true, but it would actually make wins more similar to the past because it would reflect that changing reality that starters hardly ever finish games anymore.
But the concept of a 20-game winner would then remain in baseball, whereas it is now an endangered species, and who was a 20-game winner, as he shows, would not be dramatically different than before, though it would calculated differently. That is why I wrote that it is somehow satisfying - to see a good pitcher today with a 23-9 record, instead of 16-7.
I know that Bill James was throwing around the idea a while back of 4-man rotations with a maximum of 5-6 innings pitched for a similar motive.