True, but then you would have to scan the map all the time after every turn, instead of just doing it once at the end. Also, you would have to have FoW on all the time, and you wouldn't be able to escape arguments that the game was not intended to run without FoW and that the AI is lifting sieges because it's shy or something... In sum and a priori, I don't think that the information you would get from countinuous sampling outweighs the number of trials you can do by scaning at the end. I know what you're saying, but I predict the effect size to be so large that it won't really matter.
If not, the hypothesis becomes questionable anyway. I suppose we do both. For now, we should do it as you suggested to test our hypothesis. If it is proven beyond the shadow of a doubt that the bug exists, we can explore it to more detail by investigating individual AI actions.