Coriolis effect is actually negligible at this scale, but even at full size, whirlpools don't rotate any fixed direction; their rotation is determined when they form by whatever circumstances conspire to allow them to exist, and may go either way. Coriolis does provide a bias to one direction over the other, that gets more significant the larger the body of water being drained, but to make it reliably impose its influence you basically have to start with a really huge, really circular pool of artificially still water with a perfectly-centred, perfectly-circular drain. Even at toilet-bowl scale it's influence is not noticed; our flushes spin like yours.
Even if it
was a universal law, though, you might have just been looking at the Southern-Hemisphere model.