Ares is stating that they are aware of the problem. The mats were shipped to them separately it seems. They state that they should be arriving 1-2 days after you receive the game in a separate shipment.
Rolled mats are obviously going to be sent separately in a tube. I imagine some of the boxes and tubes are going to arrive separately and some at the same time, depending on what happens at the sorting facilities along the way. Even some maps before the game box. I wouldn't characterize it as a problem, or even an issue as Ares did, but a situation. Actually, knowing that the mats would have to be sent separately is why their charges for international shipping were so reasonable and why I got three!