I really think something is off when AIP jumps up, the most dangerous thing becomes previously completly ignoreable reinforcement building up constant Carrier spawn.
At that kind of AIP you're in the range of "the AI knows what you're doing and is going to kill you (unless you have apocalyptic defenses)". The specific mechanic it uses to do it is less important
The formula is complex and would take me a long time to detail here; a quicker and more accurate way for you to see it is to turn on the Reinforcements Logging toggle under advanced (you don't normally want this on, it can be fairly voluminous), play the game where you're wanting to see the reinforcement math for a reinforcement-trigger or two, then stop and look at the log files (Reinforcements_MainThread and Reinforcements_AIThread or something like that, in the RuntimeData directory).
I'd be interested in those logs too, in that case.
