IJN has even a worse problem, a CVE or CVL that comes with a torpedo bomber that can't be produced for close to a year and can't be changed.
Anyway, back to Allies, this is obviously an error. However, the answer results in a question, because the carrier activation date isn't always the same in different scenarios. The carrier activation date, the aircraft it has, and the production availability of the aircraft should all match.
The prototype explanation has been around for a decade, but I don't buy it. Equipping airgroups with aircraft not availble for production functiaonlly makes that airgroup unavailable for combat. If an airgroup isn't supposed to be available for combat, well, then, the game shouldn't activate it!
I got rid of the uncooridnated airgroup activation/factory activation in my revised scenarios.