Take a look at the back page of a Connecticut Sample Ballot <look at the 2nd page here>
It is likely that the example shows two columns and rows is designed to be as simple as possible and by showing two candidates selected in different parties is intended to be fair (at least to the two dominant parties). But it would suggest, at least subconsciously, to some voters that voting in a ZigZag is particularly appropriate.
Note also that the vote for one example looks very similar on the instructions with two rows and columns, also showing a ZigZag pattern.
