Precisely what I suspected. They are counting on people allowing their current Game Pass Console subscriptions to lapse and then they will no longer be grandfathered into the old tier. Can't even remove it from recurring payments. If you do, *poof*, you're off the plan at the end of your time. And "redeemable until further notice" means, in the not to distant future, they will no longer allow people to redeem anything but Core, Standard, or Ultimate and any unused codes will be 'upgraded' to a different tier at a determined/reduced ratio (like they did with people who redeemed XBL Gold time cards while subscribed to Game Pass Ultimate).
Game Pass Console is all but dead. They're just hiding it in PR speak.