Charlie, Duncan, you are correct.
Interesting one isn't it?
This was actually done deliberately because of two experiences I have had of the battery switch failing. Once whilst on shore, but the worst one was whilst at sea drifting towards rocks!! Both times I was using a good quality switch.
With the switch wired as shown in the article you always have power to the motor if the switch fails. For me, on a small boat, this is more important than being able to isolate the battery from the motor. I don't think there is a safety issue with having the motor permanently connected to the battery on a small boat.
Which ever set up you use, I always tend to leave the battery switch in the BOTH postion when starting and running the motor. The only time I move the switch to BATTERY 2 is when fishing at night when I want to ensure I don't drain the engine battery (BATT 1).
With the switch in the BOTH position and the switch wired the conventional way, the charging to the batteries will be no different to the way I show it wired. The battery with the most demand will take priority on who gets the charge. Granted with the conventional set up you can isolate the charge to either battery, but I have never had a need to do this. Instead I feel much safer knowing that battery one is connected directly to the motor so that it will start.
I thnk this is a set up that works on a small boat, but wouldn't advocate it on a larger boat where the power demands are higher.
Having said all this, I'm going to change the article so that it shows the conventional set up. Getting tired trying to defend this set up. You'll just have to take the risk of the switch failing.
cheers
BF