You're actively mischaracterizing what the experts are saying though. They are saying that testing novel execution methods on a person is torture definitionally. They are asserting that it's torture even if the method is absolutely painless.
And I absolutely don't disagree that the man was thrashing and gasping for 20+ minutes. But I think it's very germaine to point out that he was thrashing and gasping for 20+ minutes the last time they tried to execute him, and they didn't even get a needle in his arm.
I'm sorry my dude, but I really think you're trying to put a spin on the facts. I'm not even arguing that it's not torture. You're literally killing the guy, right? It doesn't mean that it's not painless (physically, not mentally, obviously.) And just because you assert that that is what the experts are saying simply doesn't make it true.
Honestly, I heavily considered going and hunting out case studies on hypoxia, and everything, but honestly, I don't care enough. I've invested too much emotional effort into this already, tbh.
I will point out that Philip Nitschke is actively in favor of execution by nitrogen asphyxiation, and has even personally worked on the design of a containment chamber for that exact purpose. His only complaint was with the Alabama methodology, not the idea itself.
And I disagree with you're assessment that the point is the cruelty, but obviously neither of us will ever convince the other on that score.
Regardless my man, I hope the weekend is treating you well, and you're getting some good rest and finding peace where you're at. I'mma go touch grass, lol. Peace. :)