Sure, but is a low quality life worse than oblivion? Even if you're not 25 and healthy and wealthy and happy, I think life is still worth living.

Plus, if the suffering experienced by this patient helps cause someone else (or many someones else for centuries to come) to have a higher quality of life, one person's suffering can buy a lot of QALYs.

Alternatively if as my mother tells me, I'm doomed to an eternity of unimaginable physical and psychological torture by supernaturally powerful fallen angelic beings with complete control of my entire sensorium, even a few more minutes of being hooked up to a hospital bed with doctors trying to make things better are preferable to that!

Doctors (and society) should not be encouraging this mentality.

But individuals surely have the freedom to think like this and make decisions accordingly.

I'd wager such choices are highly personal, and different people will weigh things differently. I've seen quotes from people undergoing dangerous and highly experimental treatments stating that they felt happy to help medicine learn, even at significant cost to themselves. The patient in this case said much the same.

Nonetheless, I do generally agree with you. I've seen several articles about how doctors die very differently than most people (they often have DNRs and far fewer end-of-life interventions).