Not sure here tentatively feel free to question
But the electric machine the Alternator has one input the power going to the rotor the regulated input
that affects the output .The white ones
Green and black to the brushes
The rotor gets ca 12 V and 5 ohm 2.4 Amps coming out on the black .. ( I Believe )
That 2.4 A is distributed at the junction
from the lead coming from 9 o clock there is 2.4 a that current has to go somewhere
it can chose the wire at 3 o clock or the wire at 12 o clock
There are most likely some resistance somewhere in the 12 o clock since 2.4 A to ground is kind a big number
Say worst case poor ground the 12 o clock is open Then 2.4 Amps tries to smash into the 3 o clock wire smashing into the regulator
That can perhaps destroy it.
On paper or as the schematic the ground is ground but there will still be some resistance in 12 and 3 o clock wires
Without splice aka no 3 o clock wire then the 2.4 A Cannot smash into the regulator
the black from regulator is grounded somewhere else fex all the way to the battery minus
and