I agree that we could have been a bit more explicit. From our perspective it was “oh turn off the switch that enabled all those changes we made” essentially reverting it back to the 2.4.3 (post-nerf) state that we started with internally.
Of course, from the perspective of players clearing the content weekly, its not as obvious what we did to make it “pre-nerf” so its likewise not as obvious what gets nerfed when we turn those off. You can scour 15-year-old patch notes to try to figure it out, but we’ll try to be more explicit in the future. Sorry about that!
(We’re all busy, of course, so I can only say we’ll try our best! Time is everybody’s enemy! 
)
Regarding post-nerf stages in general, our overall philosophy was: “when the next tier unlocks we go to post-nerf,” but obviously we let T5 go a bit early so people could get attuned for Tier 6 over the holidays. Also, we need SOMETHING to trigger the nerf of Sunwell since we haven’t announced any content coming after it, so we’ll try to give you a heads-up about when that nerf is coming, but its obviously a ways off since we haven’t even released Hyjal and Black Temple yet. (Soon!)
We certainly want everybody to get a chance to experience the harder versions of these bosses as they were originally released, as well as giving people a chance to progress past them in the form the eventually ended up in.
Hope that helps clarify our intent, even if it doesn’t provide much in the way of details.