Depending on where you live Twix packaging has an end like this, which gives you a top of the package to orient yourself to. But that’s besides the point because the ad expects you to not think about it too hard and just accept a left and right twix.
Twix are chocolate bars which comes wrapped two identical pieces in one wrapper. OP can apparently tell the difference by taste which is absurd.
But that can’t be the joke because there is no inherent orientation to twix bars, so there cannot be a “left”
The wrapper is not symmetrical. You can consistently define a left and right bar of a given Twix in an unambiguous way.
Depending on where you live Twix packaging has an end like this, which gives you a top of the package to orient yourself to. But that’s besides the point because the ad expects you to not think about it too hard and just accept a left and right twix.