Would you say that someone with a disease, who does not have a good prognosis, should not have hope that maybe they'll be one of the 6% (or whatever) who beat the odds? Unlikely as it is to be in that 6%, hope gives inspiration to more effectively apply the remedies. It may still be the case that such a person is in the 94%, and such hope is false, but since the future is uncertain, what is the harm of such hope?
Of course they should have hope.
In your hypothetical, the hope is well-founded. The individual is aware their chance is 6% and they hope (and ergo, often, work) to fall within that bracket. But they're aware that nothing is shifting the scales in their favour, and they should probably prepare for the most likely and worst scenario. Their expectations are realistic and well-informed.
Your scenario doesn't really qualify as hope-through-religion/faith, though.
Imagine the patient had a superstition that a root with no proven medicinal qualities, purchased from shamans, could increase her survival chance to 94%. She'd have a lot of hope,
but it would be unfounded, and she'd not be preparing for the most likely and worst scenario. She'd be poorly informed.
The distinction between the two is the
interceding force, whether of spirits, God, ancestors, angels, rhino horns, roots - whatever. Something which has no proven impact on the situation but, through misplaced hope, is unrealistically thought to increase a 6% chance of survival to a 94% chance of survival.
Can you see how damaging such false hope could be? There are a few anecdotal examples in the last few posts here.