[uhaulball]

Cool so i was correct.

which brings me to my next question.

What is the purpose of connecting the ground wire from the sidemarker to the ground of the front blinker?

since inside the adapter there is apparently already a connection between the #2 and #12 (my dotted red line), therefore when we cut #12 we lose that connection so we need to ammend that connection again with the resistor; but now u wanna connect the front signal ground and sidemarker ground, thats redundant isnt it? since theyre connected again when you connect the front signal with the sidemarker power wire. the dotted red line is in use once again, so there is no need for the brown wire (wire between sidemarker ground and front signal ground)