Because It looks like he takes M=1 flag..for Maxwell.
Output from the miner.
[15:19:21][0x000029f0][info] miner#0 | Initializing thread #0 (CUDA-DJEZO) GeForce GTX 1080 (#0) M=1
[15:19:21][0x00001de4][info] miner#1 | Initializing thread #1 (CUDA-DJEZO) GeForce GTX 1070 (#1) M=1
[15:19:21][0x000031a4][info] miner#2 | Initializing thread #2 (CUDA-DJEZO) GeForce GTX 1080 (#2) M=1
[15:19:21][0x00002694][info] miner#3 | Initializing thread #3 (CUDA-DJEZO) GeForce GTX 1070 (#3) M=1
[15:19:21][0x00002504][info] miner#4 | Initializing thread #4 (CUDA-DJEZO) GeForce GTX 1080 (#4) M=1
Try -h and use different -cm modes.
I put -cm 0 0 0 and the gpus take M=1 (1x1080 + 2x1070) - total 560sol/s