I agree with your post on harvey, even though he doesnt really triple extend and that is obviously a loaded phrase in order for brent pourciau to help sell his product, harvey and all of the hard throwers have a common denominator: their hip to shoulder separation.
however, I think that a guy like harvey can get away with not fully extending because he is such a physical specimen at 6'4 220lbs. If you look at a guy like Bryan Villareal on the tigers, he most certainly has to use his lower half to full capacity.
If you look at the pitchers posted, they are all huge. PRice is 6'6, verlander 6'5, and Ryan 6'4. Koufax was only 6'1 and as you can see at 42 seconds, he is fully extended.
so overall I have to disagree with the original poster for the most part.