Something is wrong.
When everything is off, the voltage should be the same throughout.
Imagine this was a compressed air system, or the water supply for your house.
When all of the valves are closed, the pressure is the same throughout the system.
The only way there can be a pressure drop is when a valve is open and either there is not enough volume available or the flow path is constricted. If its constricted it will be high pressure on one side and low pressure on the other.
That battery needs charging. it should come up to at least 12.5 volts, 12.8 v if it was in really good shape.
What did the ammeter read with key in run? Anything odd?
Thge measurements are showing the same as the last time. I wouldn't worry about .1 or .2 volts - That may be within the margin of error when probing etc.
If you want to try to get more accurate, especially an anolog meter that requires choosing a scale, measure the drop directly instad voltage to ground. In other words one probe on the high voltage location (battery in this case) and the second probe at a location downstream. This also eliminates differences in grounding.
I've got work the next couple days, so may not be checking in.
Problem might be at the ring termnal. Those squeeze on auto store replacements aren't great. You may find the wire is loose right there. Original looked like this, but I'm not aware of a way to replicate that seal. Best you can do is a good crimp and heat shrink tubing.
View attachment 1716411421
The wires and connections that should be looked at are circled and highlighted. But its the R6 wire and the regulator that your test is pointing to as problems.
View attachment 1716411430