The devil speaks New Age. "Yoga is the work of the devil,” says Pauline priest Father Gabriele Amorth, founder and honorary president of the World Association of Exorcists. And Harry Potter, the literary and cinematic idol of so many children, is a testimony of magic; science is "not able to ’invent’ anything." At the seventh edition of "Peoples and Religions Umbria Film Fest," Father Amorth declared that "even seemingly innocuous Eastern practices like yoga are devious and dangerous."
-— “ Father Amorth declared that “even seemingly innocuous Eastern practices like yoga are devious and dangerous.” -—
My understanding is that in Hinduism, the positions are a part of Hindu prayer/worship. The concern is that, as when innocent children play with a Ouija board, these practices may open a door to the demonic.
At the very least, yoga-for-stretching can serve to interest people in Eastern spirituality, i.e., Hinduism or New Age practices. New Age practices are particularly dangerous.