Battery wiring - This looks wrong

Agreed, it is an issue of balance and efficiency.

That is how mine are wired, also how my Diesel F250's batteries came wired from Ford.

You only need to worry about the connection to the pod.  In your case you have 3 positive and 3 negative connections, I assume due to an electric tongue jack.  You can leave the one that runs to the other battery.  You could even leave the one to the tongue jack, since it doesn't have any "phantom load" when not in use.  There's an outside chance its switch could fail so that is your call.  Personally if you are adding a disconnect switch or fuse there isn't any extra work to include the tongue jack connection so I would.  The most important one to disconnect between trips is the heavier red wire which runs to the converter and then to the rest of the loads in the pod.  The LPG detector and fridge control board both use power and will kill the battery in a week or two if you don't.

Technically they are wired correctly because they will give you 12 volts, with double the amperage.  However, you are right that they should not be connected that way, and should be connected with the (+) on one and the (-) on another.  The resistance in those black wires, however minimal, will still be enough to prevent the battery on the left from charging fully, or discharging as much as the one on the right.  Eventually the right one will fail before the left one.

Here's the way our two 12s were wired (in parallel) as delivered.  What looks wrong to me is that the (+) and (-) to the trailer are both coming off the same battery.  I would have thought the (+) should come off one battery and the (-) should come off the other.  I'm thinking I've seen something to this effect in a previous post (maybe by CharlieM?)  This way seems to work ok but is it the "correct" way?