Mexico.. I truly like your response.
To the O/P... There is a very small resistance in the jumper wires that connect the batteries to one another and in the connections to the battery terminals.
Putting the charger and the load on the SAME terminals means the charger carries a slightly greater portion of the load when it is operating.
Now in practice, it likely won't make much difference, but it can....
One thing when you have multiple batteries in parallel (And for this post a pair of six volt in series is ONE 12 VOLT BATTERY). it is recommended that the NEGATIVE lead (Chassis ground normally) go to one battery and the POSITIVE to the other.. I'm not sure I support that, but that is what they tell me.
