That's correct, after a certain point (a relatively small number) we're unable to perceive that high. What I should've said was, they're saying the" average kinetic energy" is double that of lava - in other words what I'm really just trying to say is bringing up units was literally filler for that comment, it was an irrelevant addition, while correct nonetheless.

Edit: when you say something is hotter than something else without even mentioning units, you're not saying it's x Kelvin or x Celsius hotter ... you're just saying that it's hotter.

I don't know about the first point but who says we're using an arbitrary temperature scale? By twice as hot they clearly intend to mean a temperature perceived to be twice as hot as lava. That part was just pedantic.