I think this is true when someone dies young or unexpectedly. After a long illness though, the family has likely already done a lot of grieving, and may even be feeling something more like relief than grief.

I know my dad felt that when his father passed. I did too, but not as much as he did, because my dad was taking his dad to doctor's appointments and caring for him after surgery and generally seeing him in very vulnerable circumstances.

I just don't at all think that this is equivalent to not acknowledging that someone is dying.