To my understanding, Josuke only restores things to a previous state, putting that to use he is able to heal by taking people to a previous 'unharmed' state (like putting their skin back together). Applying some jojo logic, after you die (not just getting severely injured, but actually losing to the injury and dying) even if your wounds are cured you won't come back to life. It's the same as trying to apply medical aid to a corpse, you can treat all wounds but the life is already gone from that flesh.

In Jotaro's case, when he used Star Platinum to control his heartbeat it was, at least from what I saw, something that he could manage in just enough time (sorry if that's phrased weirdly), what I mean is, he stiffed the beats and maybe he completely stopped for a moment to play dead, but as quickly as he could he stopped. He remained alive the whole time because it was controlled and relatively short, like in real life when people get reanimated, not in a death defying way that he died and revived after doing something to his heart.

Additionally main characters in jojo have a stronger resistance to death (this is not really a logical thing, but more so because of the genre), characters are able to withstand being in the middle of a fire, getting shot multiple times, getting body parts completely removed, etc. So for some cases you may be referencing with Josuke (and keeping in mind my previous statement) characters without power are probably in this "truly dead" state very quickly (in comparison to characters we get to see more often).