Thats a big amount of travelling to cover in only a few episodes unless they're going by boat from Castelia. Wasnt there also a rumor going by magazine scans that N could leave with Plasma during one of the Castelia episodes and then Ash and Co. would catch up by the 3 part finale? It may have been said cause we know the white ruins are near Dragonspiral Tower so have Ash and Co and N together, go to Casteila then get a boat to Driftveil.
Personally there's way too much evidence that were in Casteila for the TR VS TP episode. Intros, Genesect, setting, characters present, air date.
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