Aren't pins 5 and 2 the positive and negative terminals of the coil?
Yes but is pin 5 positive or is pin 2 positive?
It usually doesn't mater. However some relays have + & - marked on them, if that is the case then they normally have an internal diode fitted, in which case it will matter because if you get it wrong you short out your supply with the diode.
If your picture is accurate then it doesn't matter what way round they are and so we say it doesn't have a pin that has to be connected to positive. So we say it has no positive input to the relay.