The "quantized continuum model" seems to be the wrong model for the difference between life and non-life. For where is the "smooth gradation" between life and death, when death, when it occurs, is instantaneous fact? A "smooth gradation" may well apply to descriptions of declining health, which may or may not result in death. But that's not what we're talking about here. We're speaking of the physical difference between the living state and the dead state. This is a stark difference: We do not speak of something as being "partially dead," after all, except figuratively (that is to say, not as matters actually stand in reality). The something is either dead or it is not.
You can argue otherwise, I suppose. But to reason thusly is to deny observation and experience. So why do it?
No, to reason thusly is to deny a Judaeo-Chritian world view. In my opinion one ought to be careful citing 'observation and experience' when what one is really citing is the dogma of one's particular religion.
We encounter people with cognitive functions all the way along a continuum, from fully alert and aware, to deeply vegetative. I would say observation is very much consistent with a continuum between life and non-life. In fact, if it were really an either/or thing, decisions whether to continue medical treatment would not be so difficult.