Proper way to Wire Solar in Parallel?

The 12 volt batteries are wired properly as shown by Roy. The reason is that you want to balance both the charge and discharge cycles across the storage capabilities of the batteries. In other words, you want to draw equally from all plates as well as then charge them equally. Physics defines the characteristics of how electricity flows...and the method shown will best balance the charge and discharge cycles across the battery bank. If you are really trying to balance the bank then you also need to pay attention to the size of the wiring and the length of each wire, but that is beyond the scope of this answer.

Solar panels in parallel are not storing power or being charged. Thus they do not need to be wired in the same fashion. Simply attaching all positives together (typically in a distribution box) and all negatives together is correct. It is best to home-run them to the distribution box, and not to daisy chain them to each other. This mitigates wiring failures better, and more importantly, it keeps within the ratings of the junction boxes on the panels.