I don't doubt that Matthew Bowman knows more about Mormons than I do. I've never bothered to do that much research on them, though I have read the Book of Mormon cover to cover. He may be right that the average Mormon no longer believes in magical undergarments but that does not change the fact that is still part of their official doctrine or that they have done nothing to mothball that ridiculous notion.
I do find his assertions somewhat suspicious since a few of the examples he gives of similar ideas among other religions are rather faulty. For the sake of brevity I'll stick with one in particular. In his "Mormon Temple Garments -- They're Not Magic" piece he implies that most Catholics no longer believe in the power of Saints. If he thinks he know Catholics as well as he knows Mormons than he is delusional on both counts. Veneration of Saints is alive and well among Catholics, and not just among the most conservative ones. I know plenty of Catholics who have various Saints medals/pendants, among other accessories. It is not for aesthetics. Most of those medals are rather ugly. Plenty of Catholics either pray to or reference saints in there prayers. Pilgrimages are still being taken. There are at least four major websites devoted to Medjugorje alone. If Bowman thinks people are visiting these sites out of sense of culture/tradition he's not only delusional he's an idiot. I've actually been to a few of these sites (ex. Saint Anne deBeaupre in Quebec, Canada) and I can tell you I was one of the few who was interested solely in the architecture/art. Hundreds if not thousands were praying and making offerings. Many were looking for cures to various ailments. Basically, his casual dismissal of things like the, "stories of the relics of Catholic saints curing epilepsy or blindness" does not match reality.
In the end, I find apologists like Bowman rather disingenuous. It is important to note how the average believer views their own faith but it is equally important to be aware of what the official doctrine of the religion they follow is and what the leadership says is essential to that religion. Criticizing critics for noting how ridiculous a specific doctrine is seems like a rather weak dodge.