When I first read Plantinga's
WCB, and came across his employment of the
sensus divinitatis, I thought, "Why is he doing that? If anyone opposed to Christian belief has been with him up to this point, they've bailed by now." However, it's important to keep in mind that he is not trying to make a truth claim. He emphasizes this over and over. He is simply trying to give a model or an account as one possible explanation for the warrant of Christian belief. The model doesn't have to be true, it only has to offer a reasonable explanation. Going back to Rowe, unless someone reads Plantinga with the principle of charity, I doubt they are going to accept his model as reasonable or having any explanatory value.
Or, think about Plantinga's "free will" defense in regards to the logical problem of evil. I heard this account in college so it may be apocryphal, but when Jerry Walls was at Asbury Seminary (think
Why I'm not a Calvinist) he criticized Plantinga's free will defense on the grounds that Plantinga is Reformed and (presumably) doesn't believe in free will. Plantinga responded that his purpose was not to argue for free will, but to come up with an argument that would function as a defeater for the logical problem of evil. Whether he believed in free will or not was beside the point.
I think his employment of the
sensus should be read in a similar vein, whether it is true or not is beside the point. Does his model offer a satisfactory account of warranted Christian belief, if it were true? Some will complain that's not how models work. But, when it comes to God and belief in God (or lack thereof), no one knows the truth, in the strictest sense of "knows." So, in this instance that is exactly how models work. Presumably, an atheist who presents her model will be given the same allowance. Can she prove the non-existence of God? No. Does her model offer warrant for atheistic non-belief, if it were true? Possibly.
See, philosophy is fun!