In Polish cz, rz, dz, and sz are very common, like sh and ch in English. Look at your US style keyboard and notice when typing ch and sh it is a L followed by R hand press. Now look what happens when you want to enter the common Polish cz, dz, sz, or rz. They are both L hand. So that's why Y and Z are better swapped for Polish language. L and Ł are better to be two separate keys because often there is only one modifier key for the letters with tails and it is on the right near the L key.