Is PS Against Using Scientific Arguments as Evidence for God's Existence?

That is my understanding as well. Frequently the DI has said that it is within the competence of science to determine whether or not design exists in a given organism, system, etc., but not within the competence of science to identify the ultimate source of the design. So any conclusion that the designer of the flagellum or the camera eye was the God spoken of in the Bible would not be a scientific conclusion and would not have the blessing of science, not even science in the extended sense (extended to allow design inferences) allowed by ID proponents.

Of course, human beings are not always scrupulous in the way they argue, and some ID fans may write loosely about how ID establishes Christian truths, but when they do that, they are mixing up apologetic interests with ID theorizing.

I see the main value of ID for Christian belief or theistic belief in general as a ground-clearing one; ID challenges the claims of many atheist champions of science that “science has proved there is no God” or “science has proved that the world was not created, but only evolved,” or “only stupid or ignorant people could believe there is design in nature.” It thus removes some objections to religion that are running around in the popular culture. But it doesn’t make a direct positive argument for any religious belief, and it can’t do so, given its limitations.