My seriously NPD friend of 40 years very frequently talks about "spirituality" in the classic N manner, and I think it is probably very typical.
When he can get N supply directly from people, especially women, the talk about spirituality suddenly stops. He even makes fun of it. Then, when the N supply runs out and he feels isolated and depressed, spirituality is considered. And it is a way, I believe, to feel superior in his own mind because he either says directly or infers that he has special spiritual insights that few people have. And he also tells me that I am just on a spiritual path. No matter what I am considering or doing, it is this "spiritual path." With the spirituality, he now can be omnipotent, direct my life, and see how people around him are so empty and inferior.
In short, I think the N's spirituality is another tool for supply.