Aside from the people being purposely obtuse and/or vomiting up the word nightmare...

This is something entirely possible over the course of an expansion as a side project just like many additions through the years have been. They don't have recreate the scenes/animations/cinematography 1:1, just give ARR-style versions with the emotes and waist-up rotation-walking (since turning animations were uncommon then) and condense it into a maybe 2 hour (tops) greatest hits style of story beats that culminates in a solo trial against Nael on Rivenroad and then auto-plays the ARR intro that we know so well.

And they've a myriad of setpieces and zone sections that can be used to approximate the locations in 1.0 with the exception of some extremely notable spots near the end. And as for them taking all the lore that still suitably fits into ARR, that includes the 1.0 MSQ. Non of that is non-canon so it's not like they'd have to explain some weird story oddity that has been left behind or retconned, and the only real lore hiccup would be if you aren't a Legacy character that defeated Nael originally but did so in NG+ and they still refer to the WoLs as someone else instead of the wink and nod those subset of Legacy players got.