To those users saying "But this was the case with SOTO, you should expect that to continue" I can certainly appreciate that. I think that's entirely reasonable for Anet to place some rewards behind the latest expansion. However, I feel the past information on this is now coming across as misleading and in some ways as making false claims.
Per their previous published articles on the topic:
"Once one of your characters reaches level 80, the Wizard’s Vault UI will be accessible to all characters on your account, regardless of which expansions you own. If you do not have Guild Wars 2: Secrets of the Obscure registered on your account, some rewards will be locked, and you will be unable to visit the in-game location of the Wizard’s Vault. The system will be fundamentally the same for you otherwise"
Note however that the information does NOT say "if you have not unlocked the latest expansion, in this instance Secrets of the Obscure, some rewards will be locked."
Therefore this previously published statement may have been misleading and did not hint at existing rewards ever being locked in future to later expansions. If I was aware of this being the case, I would have considered this in my purchasing decisions.