...............That picture is wrong. There should be no connector between the "2" terminal and the B+ on the back of the alternator. If you do that, it works just like a 1 wire..
That statement is true to an extent. "One wire" also means "self exciting" IE there is not switched 12V to the no1 excitation terminal
But if you have a normal front battery, and a direct, LARGE no6 or bigger charge wire and short in length to the battery, the jumpered wire to no 2 will actually work OK for sense.
I DO agree with you, though, I don't normally care for one wire setups or "local" sensing, as the BATTERY is where sensing belongs.
As I eluded to earlier, proper sensing is how I set mine up --long before, by the way, that Al Gore invented the internet
The thing which originally "got me" into using Delcos is that I blew up a couple of Mopar alternators. On my old six-pack 440 car, the original factory pulleys on the crank/ alternator, put the alternator at over 4:1. This means that if the engine is cranking 6K, the alternator is spinning 24000 RPM!!!!! I had a 70 Cuda for a short while, a low budget "run what ya" deal, and ran 5:38s with tall rear tires. That thing went 7K + through the traps.
The mechanical failure mode of the Mopars is, that the cases seem to "work" a little and the vibration can wear notches in the case machined lands where the stator sits. Eventually, this mis-aligns the stator somewhat, and either the rotor slightly ticks the stator, or it begins to vibrate. This mechanically wears the enamel right off the stator windings!!!!
"Back then" I've seen a number of these fail in this manner. If you look at the alternator in darkness, and goose the throttle, it looks like a mini - lightning storm in there. The stator windings arc across to each other.