Ive run numerous non tubeless tires (high rollers, nevegals, minions, butcher sx to name a few), sooner than later I'll put a hole in the tread and sometimes sidewall that is too big for the Stans sealant to plug. I even put a hole through the tread on a pair of Conti tubeless mtn kings. I'm not a hack I swear! haha. I found on some tires it may take a few days for the tire to seal around the bead. Lots of shaking and reinflating but Ive always managed to get a seal, and this was on a dt 5.1d rim with a stans conversion kit.
The one exception is the Butcher Sx I had mounted tubeless on the rear with a Mavic 823. Worked great and never a flat. Just slow rolling for the summer I found.
Is the tire casing on the HR2 thicker than the HR?
I guess actual mileage may vary
I also don't put the hours or abuse on that some people do so maybe I just have better luck.
But chances are if you put a hole in the tread or sidewall large enough that the sealant won't plug it, you'll have also punctured a tube so you're really not in a much different situation are you? Other than it's a bit messier to put a tube in.