How can you determine if his chain is too long or too short from that picture? In order to see if his chain is the correct length you must put it in the big chainring and the smallest cog in the rear and see if the pulley wheels are 90 degrees of one another.
Its just a guideline that will work with some but NOT all chainring and cogset combinations. It will work well with a standard 39/53 and 12-25 setup. BUT ... try doing it on a 36/52 and 11-28 setup and you get into problems ...
You still need the "small-small" combination check for sufficient chain tension and the "big-big" combination check to check for sufficient chain length (and prevent unnecessary strain on the RD at extreme crossover) to be 100% sure.
If you've wrenched enough bikes ( be it hobby or as a job), you'll see all sorts of funny permutations and their quirks. Most of the people here are making a judgement call based on our own experiences. And why not you wait for the original poster to come back to verify our prognosis instead ??