EDIT: The second instance of being flat-footed I was referring to was entering intense diplomatic dialogue with China in an attempt to get them to avoid making any concrete commitments, and then discovering (based on direct and indirect feedback during talks) that China is already much further down that road than we assumed.
Russians would know very well that MiGs are flying from Poland no matter whether they would go trough Germany or not.
And they would have to track them precisely in order to attack in both cases as well.
The stupid part was going with the MiGs transfer public in the first place back at the beginning of the war.
But I recall it came from EU official and Ukrainians, not from Polish government directly.