It depends, but I’ve definitely done it both ways. By the end of my Clone Wars series, I was absolutely editing the longer arcs which needed less radical changes back to front in five minute increments, and I found I could basically edit the entire episode to a great standard in a single pass. But by then I’d done dozens, so doing things like polishing transitions in the moment (rather than all afterwards) didn’t interrupt my flow.

Andor was a different beast. Definitely the planning for each arc was done back to front, especially with all the content that ended up in the final episode. Those required far more shuffling around though, and perhaps 90% planning to 10% execution, since there was just so much shuffling to do.

But yes, it’s absolutely viable. For your twelve-in-one edit, so long as you’ve identified what your ending needs to be, and perhaps put that together so you know exactly how it feels, you could totally just rewind through the show from there. You’d probably need to revise it a few times after (I always put cut content to one side until I’m certain I’m finished), but I find that the process really helps me judge whether or not a scene or a moment belongs.

Pick your payoff moment, then choose all the other content that earns it.