Asked in a comment weeks ago and never got a straight answer, so putting it in its own thread.
Digital preorders through the console stores include a month of GTA plus. If you already subscribe, does that extend your existing term, sit unused, or start when the current one ends? Nothing official addresses it that I can find.
No official answer exists. Subscription bundle terms are usually in the store fine print rather than in Rockstar's material, and the fine print for this has not been detailed.
That is a useful data point even with the caveat. If it is a separate entitlement then it presumably queues rather than stacks, which is the normal behaviour.
mine did the same thing. it sat there as a thing to redeem rather than adding a month
Two regions agreeing is enough to say probably queues and not enough to say confirmed, which is where most of what we know lives.
Mine showed as a separate entitlement at preorder rather than an extension, but that is one store in one region and I would not generalise from it.