No, I think they meant what they said: we can encounter the situation where 50% of products need to be separated out only because some molecules are chiral. (Ac

No, I think they meant what they said: we can encounter the situation where 50% of products need to be separated out only because some molecules are chiral. (Actually their comment was extremely carefully (and well-) worded for a social media comment!) See, in general your statement that reaction products can be mirror images of each other is true for most of the chemical reactions humanity has been able to produce in a lab/factory, yet many reactions don't require separating out 50% of the products because it doesn't matter that they're mirror images if they're non-chiral molecules. Think of the (non-chiral) letter H: a right-handed and left-handed letter H are the same -- one can always be rotated to match the other. The only time it matters that most of our chemical reactions can produce either left- or right-handed molecules is when these molecules are actually different, meaning they cannot be rotated to match each other. Think of the (chiral in 2D) letter L. There's no way I can rotate the letter L in 2D space to make it match its mirror image. (Of course I can if I'm allowed to rotate it through 3D space.)