That still doesn't mean the movie can't happen in that timeframe, minor nitpicks regarding previous interactions between characters don't contradict Kubo's clear intent of canonizing the movie, this has happened all the time in bleach actually (hell's retcons,the plot changes and inconsistencies broguht by the TYBW arc, minor stuff like Gin stating he never said Shinso's/Kamishini no Yari's ability was about extending and retracting when it was stated on both the manga and official databooks) this kind of stuff happens all the time, Kubo decided to reference the movie, and even Ganryu's clan hiding in both the manga and novels, the intent of canonizing it is quite clear