Annual plan should equal 12x monthly credits, not a reduced quota.
It would ensure the discount affects only price; not usage, and thus incentivize getting a yearly plan.
I chose the annual plan specifically to save money. As such, I'd expect the total value of credits to be at least equal to what I'd get by paying month to month. Right now it feels like the annual discount is partially funded by reduced AI usage credits rather than a billing-frequency discount, just like in most other services.