A key point in the previous post discussion that I have somewhat overlooked, is the fact that the research team are investigating brain oxygen. That is, blood flow during cardiac arrest is not the focus, nor indeed is blood oxygenation, but the brain oxygen levels are.
So perhaps some patients’ brains could have a more advantageous oxygen storage / depletion ratio, and therefore sustain less immediate damage, and so possibly maintain better functionality.
If found to be so, then it could be that a minority of people have a better prospect of brain functionality during a cardiac arrest, and therefore possibly a better chance of survival. It could be that these people because of their brain functionality, remember experiences when they wake up.
Seen this way, the study is not really looking to challenge any conventions after all, but more exploring a possible minority scenario that may exist in cardiac arrest cases. The idea that brain functionality completely ceases within a few minutes of arrest as an absolute rule is what may have to be reconsidered.