I am with Steve on this one. I think the term caused a stir because camera nuts in the West were obsessed with sharpness, resolution, lines-per- mm etc. Those measurable criteria were the subject of all the lens reviews, such as they were. And here it turned out that Japanese photographers were looking at the whole picture, not just the subject, and had come up with a vocabulary to describe what they cared about in a photo.
I think the photographer is responsible for everything in the frame, and so encountering the term was, for me, a revelation. I was one of those camera nuts who thought that subject sharpness was the end-all.
I understand the dismissiveness in Nick's post above - I did the same thing in a post here about bicycling with a camera yesterday. It comes, in my case at least, with impatience with convention. But I think the OP's question is a fair one -- after all not all 50's are created equal on this score, and why wouldn't a photographer want the input of other actual users of a particular lens before purchasing one? I believe it is not just the elements of lens design, but also the aperture shape that matters here.