Proof of pass ownership provided in the link above
As stated here, https://www.bungie.net/en/Help/Article/48522 future season pass owners should have access to the questline, the only issue is that the game requires you to have the season 8 pass specifically, denying season 9 pass owners the final strike.
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Same problem... and also Bungie / Activision its the most scummy practice in games to put your exotics behind a pay wall in the first place...