I disagree about that, at least to a degree.

I believe it's good to stretch out very carefully and controlled after a workout, but
the single most important thing is to easy run / jog out, so to increase the blood circulation which takes care of removing the waste parts (in a lack of a better term) that derive from the muscle activity. 10 minutes should be sufficient. However, I see many people stretch, almost frantically, in a wild manner, because it seems like the efficient way. It's not. At least if you have had a heavy workout for your muscles. For those types of workouts, tiny fibersized wounds open in your muscle fibers (which is perfectly normal, the restitution process is mostly about 'fixing' these wounds, and enhancing the structure). When you stretch out heavily afterwards, you also stretch out these fiberwounds unnecessarily, and in most cases, unfortunately. Careful stretching, fine, but if you push yourself and feel that you are 'stretching in an efficient manner', that's a no-no.
Stretching for the sake of softening up your muscles for the long-term (man, I really run out of good words now..) can be done after you have warmed up easily..
This is what I have learned from a renowned sports physician, but I know his opinion is not the end all be all.. It's just that I also intuitively think it is logical, so I choose to stand by that view.
Edit: I realize I might be misunderstanding the type of stretching out you advocate...? Depends on if you mean thoroughly is pushing your stretch limitations of your muscles, or carefully stretch out for a longer time period..