Pretty sure the special orders are for things like bags in combos that they don't make, like the District MM/PM in Damier Cobalt or the Dayton MM/PM in Monogram Eclipse or Damier Cobalt. Perhaps LV would approve making those bags in those canvases as a special order, though.
Special ordering past collections, though? I doubt LV is going to go there. Otherwise, they'd be flooded with people wanting bags from probably every single collaboration they've ever had--imagine how many requests they'd get for items from the Supreme collection alone--and it would make those past collections less special.