STV isn't a "subset" of STV. STV can be used to select X winners out of a group of Y. If Y is 100, and X is 5, you call it STV. If Y is 100 and X is 2, you call it STV. If Y is 100 and X is 1, you called it "IRV" -- it's still STV.
The same is true of Range Voting and Reweighted Range Voting. If you use RRV to elect 1 winner, it's just the same as Range Voting. One could just dispense with the distinction, except that you might pick, say, a school board by holding six regional single-winner RV elections, or you might do it by having ONE multi-winner RRV election. But IRV _IS_ STV, make no mistake about it.
no subject
The same is true of Range Voting and Reweighted Range Voting. If you use RRV to elect 1 winner, it's just the same as Range Voting. One could just dispense with the distinction, except that you might pick, say, a school board by holding six regional single-winner RV elections, or you might do it by having ONE multi-winner RRV election. But IRV _IS_ STV, make no mistake about it.