> people with the vaccine presenting at hospital are more likely to survive than those presenting without
In my opinion, that logic is flawed.
The currently available COVID-19 vaccines vastly reduce the likelihood of developing severe symptoms from a SARS‑CoV‑2 infection. They also somewhat reduce the risk of getting infected in the first place.
So, getting vaccinated against COVID-19 makes you far less likely to need to be hospitalized, should you contract the virus, which apart from of course being beneficial to yourself also helps with keeping the healthcare system from being overwhelmed.
However, if you've already been hospitalized, it is because you've developed severe symptoms, which in turn means that, in that situation, for you, the vaccine has failed.
At that point, all other factors being equal, your likely outcome is no different from that of a person who hasn't been vaccinated. Therefore, using vaccination as a criterion for triage (which - like you said - is all about rationing resources, not passing judgement) doesn't make sense.
Now, it could very well be possible that being vaccinated improves your outcome even once you've already developed symptoms sufficiently severe to require hospitalization. However, I'm not sure there's conclusive evidence suggesting that is indeed the case.