We see the aftermath of that fire, it's that burnt out town at the start of the zone when you enter from Lakeland. So the events of the Shadowbringers trailer were in the time between the Scions arriving and the WoL arriving.
They can maintain the collision boxes. If you looked at the bubble between 3.0 and 3.3 there were a bunch of rocks jutting out that you could land and walk on, these rocks were removed and replaced by the external bits of Alexander after the cutscene where he stands up in 3.4.
