Unfortunately you are right, which is why I was none too pleased to hear that one was not performed, especially as I both specifically requested it to be done, and because they promised me several times that it would.
With regard to the mustang dyno question, a quick google search finds that on the S65, there is a rather large spread on the mustang, with stock whp ranging from 305 all the way to 360.
http://www.s65dynos.com/
Next week I'll be taking the car for a dynojet readout, not to flatter myself, but they seem at least to be a bit more internally consistent with each other, as to compare apples to apples, and not apples to bricks (poor attempt at a bit of humor)