1500W? At 12V that's 125A - That is fucking dangerous! Most sockets are rated at 20A. Most inverters that are >300W use crocodile clips, or preferably screw-down terminal rings. The cable looks way too thin too. That's a fire waiting to happen....
I sort of suspect that they're lying. I feel like that cable would just melt if you put 12V/125A through it.