'68 Barracuda - charging system questions

No. The only difference is you've thought this longer than I have, or should say I did.

Current flows to the battery when the battery wants to be charged.
Current flowing to the wipers never goes through the ammeter unless the alternator can't provide it.
Current flowing to the lights never goes through the ammeter unless the alternator can't provide it.
The fluctuation or discharge we see at idle with lights, wipers, and brakes on is when the alternator can't provide all the power at 14 Volts.
Alternator's potential to make power is very rpm dependent.
When an alternator is maxed out, voltage drops. When it drops to battery voltage, the battery becomes the highest voltage power source. Current flows out from the battery to the devices.

A characteristic of the battery is that it can carry a surface charge. When a fully charged battery is connected to power source at 13.4 to 15.0 Volts it develops a charge above 12.8 Volts. With a voltmeter on the battery it may show 13.0 Volts or higher when the power source is removed. The surface charge has little energy in it. It disapates slowly over time or quickly when subject to a load (flip on the lights for 20 seconds or so.)

If current flows in the charge direction through the ammeter goes to anything but the battery something is wrong.
The only thing that should be on the battery side of the ammeter is the battery.
With a jumper wire between the alternator and the battery positive, charging power should go right to the battery. There should no longer be flow to the battery in the original feed/charge line. Only flow in that line should be discharge (when starting) or when the alternator can't supply the power.