If it is yours, call it whatever you want,no matter the size.
Exactly, for now, it's still a free country.
Human nature and ego enter into the question. As might already be seen in this very thread, anything smaller than what you own isn't a "real ranch".
And, because of vast variances in value for different parts of the state, the size, in itself, has no bearing on the dollars it's worth.
I've always considered "ranchette" to mean something in the 10 to 50 acre range, and comes from a developer-busted up ranch. We always called our 130 to 160 acre places around Fbg. "farms", even though we didn't farm, nor has there been cattle in our family for 4 generations.