Trouble with this sort of thing is the subjectivity of 'what chord is this?', taking into account inversions and the like. CMaj7 has C / E / G / B? Who says this isn't Emin6 with the 6th in the bass? It'll depend on the way it's heard and its context within the song, but many approaches can impact this sort of thing.
EDIT: I wrote this without carefully reading the article (oops!). Author does a great job with the "adjustments"...I suspect adjusting to relative minor covers a huge amount of these issues, and the author throws in mixolydian for good measure! There will always be edge cases, secondary dominants, modulations, blah blah blah, but I suspect adjusting to include relative minors handles the vast majority of popular music.
EDIT: I wrote this without carefully reading the article (oops!). Author does a great job with the "adjustments"...I suspect adjusting to relative minor covers a huge amount of these issues, and the author throws in mixolydian for good measure! There will always be edge cases, secondary dominants, modulations, blah blah blah, but I suspect adjusting to include relative minors handles the vast majority of popular music.