They aren’t heirloom gear as we know it.
While I would have rather had gear that my main could use, the idea is a cool concept. Level 0 requirement gear that doesn’t scale with your toon. So I can pass it along to my newest toon, but they’ll outgrow it by level 20. It gets you through the times where your toon isn’t fully realized yet, and by the time you can really hang in there, you no longer need it.
IMO, this is what heirloom gear should have been from the start.