This is pretty funny - obviously not a lot of thought went into that photograph.
However, I have used this technique as a picture-framer to get more accurate measurements. See how the top of the house is lined up with the 3" mark? He could be subtracting 3 from the bottom measurement. Often the metal clip doesn't provide a reliable stop, so that laying the tape a few inches offset and then subtracting that amount works much better.
Most likely though the photographer just thought it looked better this way.