This makes sense to me. The manufacturer listens to his pieces during development on the stock footers, and the component is voiced on that support, soft rubber footers mostly, and then on presumably a solid stand. We buy the component and then play around with the voicing in our own systems and see if we prefer the sound with some other footers.
I understand David's point, and I agree that most of the after market footers I have heard homogenize the sound and move the sound away from transparency. I can take a long time to recognize this, or it is heard immediately. The challenge I see is how does one know what is happening unless he makes the effort, often considerable, to hear a number of alternatives.
Then, as Micro writes, is it simply our preference, or something more objective, a move toward more transparency? This is becoming an area of interest for me, and I can not deny being somewhat influenced by what Tang and David have been writing. At the least, I have been listening with what I hope is a more open mind toward this stuff.