This: "Introducing IRV into the general election would make the Primary superfluous."
... claims far more than this: "So, under alternative voting you can have a Louisiana Primary."
You can have a Louisiana primary, but that does not make the primary superfluous, since the primary purpose of the primary is to select the party nominee by a more democratic process than branch membership committee selection or central party committee selection.
You cannot render something superfluous while failing to accomplish its primary task. I've been accused of being a Marxist, yet while Harpo's my favourite, it's Groucho I'm always quoting. Odd, that.