Do AIs have to take turns?

I’ve seen some AI behavior that has been bugging me. It seems like, in some turn based games, that AIs can evaluate and launch orders between jumps of the clock. At least, it seems like some AIs have responded to attacks after I have launched at the turn. I expected to have an 8 h lead, but 2 ticks into the turn they have launched to defend, giving me only 2h of lead. If they were anticipating an issue, I would have expected them to launch at the turn as well, but the delay suggests a response to my moves.

This is unprovable from the outside, so someone with more knowledge of the internals would need to answer. Am I crazy or has anyone else noticed this?

The AI makes moves every 4 ticks, I believe, no matter if the game is real-time or turn-based. It is indeed an advantage for the AI in TB games