I think the suggestion is for it to be optional. So you don’t have to turn it on if you don’t want to.
While you paid and played in prior expansions - not everyone has. Going back to those zones, dungeons, and raids is kind of cool once you’re max level for xmog runs - but it’s not challenging and definitely not the same as playing it when it was current challenging content.
This would allow players to be able to go back, turn on the functionality, and not over power the expansion just because they’ve hit max level so quickly.
This gearing system goes in parallel with the idea: Gear System Post Level Squish