The cut sheet says the PlugTail conductors are #12 THHN copper conductor, 6" leads, stripped, solid or stranded and rated as permanent part of the device.
It looks a little odd at first, but thinking about it further it should be all right so long as the actually connectors are tight.
It looks as though they might be a slight variation on the 1/4-inch spade terminals which are common in automotive applications. The latter stand up to high-ish currents at low voltages, with lots of movement and vibration.