Survivor Coop bug?

In the survivor coop games that I've played, all players work together and place towers on one shared map. Tonight I have experienced the survivor coop game mode being played by two players on separate 32x16 maps, as if they were against each other, but once the game ends, there is no skill exchange or winner or loser. When the map selection is set to random, and there are two players (one on top one on bottom), the map selection may select a 32x16 or a 32x32. The reason I bring this to attention as a possible bug is that when two players each have their own field there is no "Coop" between them, it is just a single game of survivor, which seems weird. It might be meant to be this way but I've never seen it before and it seems weird. I did a few tests with an alt and took some screenshots.