Is this relay datasheet incorrect? (Omron G6SK-2)
Omron relays that have polarized coils use internal magnets to help activation: -



Taken from here.

I suspect that a latching relay does not have a permanent magnet because it would "help" activation in one direction but be a problem when un-latching.

Hence, a two coil latching relay can probably be driven in reverse quite naturally. If you also look at the activation currents for the standard 5 volt coil version versus latching you will see that the standard requires 28 mA whilst the latching requires typically 40 mA. This kind of substantiates what I'm suggesting.