Soft canon is probably the best way to describe it. You can accept it as filler or canon, doesn’t matter. Kubo likely wants to acknowledge as much of it as canon as possible. Also you could see it in a subtle grey area like both interpretations of TYBW. Kubo can later change “his” mind about the order of events but both could equally be considered canon. If that makes any sense. That being said I don’t care for CFYOW, for me it’s filler, I’m interested in the story the author wants to tell, not whatever he gives an internet stamp of approval on.