GT-R MFD (Multi-function display) reverse CAN Bus data?

Hello there hope all is well!

-I know this is old but I came across this thread from you and a fellow QX70 owner discussing CAN bus signals:

https://www.2carpros.com/questions/pin-digram-for-speedometer-cluster

-I've been questioning all day what this person did here:

https://www.reddit.com/r/CarHacking/comments/1goavn8/nissaninfiniti_can_bus_reverse_engineering_to/

-He was able to modify the firmware on the nav unit to get the GTR MFD, and then get any available CAN bus data to transfer into the MFD tab on the now "modified" unit. There's more videos on his YT channel of him testing it if you can check it out.

-Here's where everything started:
(Guy from the first reddit link above perfected the MFD menu and translation into the united that this person "unlocked")

https://www.myg37.com/forums/audio-video-and-electronics/301371-modding-the-oem-navigation-head-unit-gaining-gt-r-mfd-and-other-functions.html

They have confirmed that it should work on every unit from 2010 - 15 I believe, but he is perfecting it on his G37 first.

Now, my question is, where is he pulling/tapping into to get CAN bus data from to translate it into the MFD to be viewed on the unit like he shows on this videos?

He doesn't really go in depth except for what he uses to data log for testing purposes on a dummy unit, plenty of instructions online on how to do that.

Sorry if this is too much to read, I just got really intrigued from all the diagrams, and detailed info you were giving on that old thread. Pretty similar but different situation here.

I'd appreciate any info you can provide and what are your thoughts on this project. For reference I have a fx50 2013.

Thank you!!