What I have seen has been similar to the above. I think that has to do with the bombardment turns, when they are split (ie: TURN 0:5 vs 1:3). I do not know if this explains this properly. But it seems like after the main artillery bombardment, the following turn follows the bombarbment positions on screen without actually putting down rounds. Possibly because all of the rounds where put down on the initial turn. I have mostly seen this when there is a third turn to the overall bombardment. And with lots of artillery.
