I don't think you're nuts at all, you're just technical, and that's really a good thing. You are looking to know what really is correct, not just what everyone says is correct. It's like all those people who call tomatoes vegetables (they are actually fruit). Look at all those people who praised the adjustable rate mortgages; they were great, until the "adjustable" part made itself known. The point is that it is great to obtain a correct knowledge, even (sometimes especially) of terminology, even if it is just for your own benefit.
Now, there is something to be said about "making things unnecessarily complicated by the use of big words." (it was a prominent literary figure who said that, can't think of his name) I'm not saying that "humus" is a large or scientifically obscure word, but it is a word that most of us do not know the true meaning of. Most gardeners, when they hear the word "humus" will think about anything that is rich, black, loamy, and usually found on the forest floor. While they may or may not be correct in thinking this, they probably do know know what truly justifies something as being humus or not. If I'm in a room with ten people who are talking about composting and referring to their finished compost as "compost," I will probably do the same. Although I might insert how finished compost is actually humus, I won't just start calling it that and have everyone wonder what I'm talking about.
In the end, It's good to know the proper word for something, the additional, commonly used words for something, and the proper circumstances in which to use each of them.
How I took something this simple and turned it into a philosophical essay I'll never know.