ICStats on 06 March 2017
In practice it looks like the left Joy-Con's antenna is partly obstructed by metal in the controller which is going to make it's signal kind of directional. The geometry of your room, anything that obstructs the signal, and anything that may help bounce the signal towards the unit may affect your results.
It's weird that the Joy-Cons have entirely different antenna designs for left & right units.
It's also possible that not all left Joy-Cons are the same; they may have already been fixed and some users got the old & broken design. Or... perhaps the one with antenna built into the circuit board is the "new & broken design" since that is likely a move to reduce costs.
My 8th gen collection
