I have two different letter templates in one TX-06 batch. What's wrong?

Nothing's wrong. This was intentional. For this experiment, we’re using both our standard “please vote!” template and a new “vote tripling” template. Since we need both types of letters to be sent in roughly equal numbers, all of the letters are part of a single campaign, with the template assigned at random. To keep things simple, the usual "I vote because ..." prompt is used on both templates, so there is no need to distinguish between them or adjust your handwritten message for one or the other template.