I guess it's a matter of lore interpretation. Combining nature and holy seems very odd to me. I feel like nature beings are too wild and untamed for holy who are so straight-laced and lawful. Nature is all about sprawling, wild growth. Holy dudes are the kinds of people who would keep the grass on their front lawn uniformly trimmed to a height of 2.5 cm.
Nature + undead makes sense to me though. It's what happens when nature goes bad!
Remember that scene from Snow White?