I would point out that in Apple's iOS case, the sliders are always consistent in two ways:
- The slider always displays the current value. So the UI reads quite naturally: "Airplane Mode is OFF".
- The "Off" value is always without color (gray, matching the background of the UI), and the "On" value is shown with a vivid color, indicating it's active.
I never found them to be confusing in iOS myself. But consistency is very important so that you don't break the user's trust.
This is a case where Apple got it wrong and everyone copied Apple anyway because Apple. Seriously though, I'm not sure Apple invented these switches but they sure helped popularize them. And yes, I do think they are terrible.
I think that's the post you are referring to. He sums up nicely why this standard style of 'on / off' slider is a terrible UI choice.