[Bug possibly in FE too] Enemies fighting off-screen

So I attacked an enemy city that had some other units standing nearby the city tile.

During the fight I noticed this:

Units that weren't stationed in the city itself joined the fight and the only way to attack them was with ranged attacks, as the usual "battle grid" was limited to the city map as usual. I think I've encountered this bug before in FE but forgot to post about it.

It doesn't seem like an intended feature.