It doesn't account for any details, or even most of the broad strokes beyond one.
It accounts for how a supernova could destroy Romulus unexpectedly. The
Countdown version and the implied movie version requires, not only that the radiation travels faster than light, but that it somehow
accelerates after the supernova so that Spock gets there too late. It's beyond incoherent. The PIC version is simple and elegant. It was Romulus's sun, they had years of advance warning, but they couldn't predict the exact date of detonation so Spock was too late.
Spock could've saved Romulus, but didn't. PIC's version makes that impossible.
Not really. If the Romulan sun had been sucked into a black hole before the supernova (assuming the fanciful kind of "black hole" depicted that can suck in such a body quickly and without spewing out a lot of debris), then the planet and its people would be intact. After all, from a distance, a black hole's gravity is indistinguishable from any other gravity source of the same mass, so if it sucked in the entire mass of the star, it might have a comparable mass to the original star. So the planet's orbit might not be seriously affected.
The planet would be in danger of freezing, but it would give the Romulans more time to evacuate, at least, and their world and the artifacts of their civilization would still be physically intact for future reclamation. That does fit the letter of Spock's line that he would "save their planet." Perhaps some artificial means could then be found to reheat the planet, maybe by increasing its tectonic activity so it's thermally warmed from within; or the cities could be encased in life-support domes. Heck, if there's a black hole there, just keep dumping matter into it and the accretion disk will generate heat and light. It'd be tricky to calibrate to make sure you didn't produce too much radiation, but it's conceivable.
PIC, by leaving a Spock-shaped hole in the backstory (probably because their revised version defies any sensible interpretations of ST09 on a plot or character level), leaves it ambiguous if he actually did somehow limit the destruction, and how that might've affected Picard's own feelings on his role in the disaster.
So what? That wasn't the story they were telling. The job of
Picard was not primarily or exclusively to explain something from a different story. That's not what storytelling is for. The clarification it provides to the movie's backstory is a
bonus, not the exclusive purpose of the exercise. The responsibility of the people telling a story is to
that story. Anything they draw from
other stories is only of value insofar as it serves the current story. If it doesn't, then it's just a distraction and shouldn't be brought up.
If he did, the actual functional means by which he did so requires the exact same handwaving and technobabble as the version presented in the movie because he's still containing an explosion that already happened.
Which, again, is the movie's problem, not
Picard's problem.
And the explanation someone mentioned above from
The Autobiography of Mr. Spock, that Spock released the Red Matter moments before the supernova and it went up before it got there, is good enough for me.
Here's the thing. They way you feel about the emotional reality and motivations of a space explosion needing to be consistent with astronomy are the way we feel about Spock needing to be consistent with the things Spock says and does. So now we're left with a frustrating question that you seem hell-bent on superficially handwaving away in a way that doesn't actually make anything fit better.
Here's the thing: I'm not responsible for your satsifaction any more than you have the right to attack me for mine. We're individuals entitled to appreciate fiction in our own ways. You don't have to like PIC's version. I'm just saying it's unfair to blame it for the problems with the movie's supernova story just because it didn't fix them. It wasn't PIC's responsibility to fix them, just to use whatever bits of it were useful to construct its own narrative.
This is getting way too heated. We've all said our piece, so let's step back and move on.
