I had to search for that Lew Bryson story and found it here: http://www.drinksforum.com/beer/Lewis-on-decoction-1788-6.htm
"Just to horn in... We were at Weihenstephan back in December, and got a
lecture from one of the profs there on this. They did a decoction and a
non-decoction batch, otherwise identical, then put the beers to a tasting
panel. They could not taste e difference. The prof was shocked, but pointed
out that while the panel could not...he could, blinded, repeatedly. He's
still a decoction disciple, but he's not sure what's going on. Is it subtle,
or is it not recognizable?
It's the last sentence that might be key. I have heard that from others as well that decoction might be too subtle to taste unless you know what you are looking for. And based on my reading it is not so much an increase in melanoidens as it is an increase in tannins and other grain compounds that come out during the boil and make the beer taste more "robust". I though that I did notice this in my last decoction experiment but when I did a triple triangle test (3 triangle tests done blind) I was not able to discern the beers.