I have disconnected the EMMC and the battery and plugged it into my PC with tegraRcmGUI running and it did not recognize it in RCM. I also just got in a new RCM jig so tried putting it into RCM with the jig in the right joycon slot + vol. down + power and did not get a result. I unplugged it from my pc and in diode mode I got the following readings
D+ = 1.492 V
D- = 1.51 V
I did this by connecting the black probe to ground (you marked in red) and the red probe on the D- and D+ pins. I am not sure how to interpret the readings I got. I am able to post pictures now so I included a picture of the reading. My USB C charge reader is coming in late, so I will upload info I get from it as soon as it comes in.
Edit: updated picture to a more detailed one