Afaik, coir does contain nutrients...that's precisely why it's not an ideal casing material. It's not as nutrient-rich as manure, but it does contain some nutrients.

As to your comments on perlite..."almost never" seems like an awfully strong statement to make, as probably no one could claim such widespread knowledge to speak in such absolutes. But hey, that's just my opinion. I certainly would not advise it (nor did I), nor would I claim that it outperforms anything (nor did I). That said, I have attached a picture from my early days of experimentation...make of it what you will