The Surface Book 2 doesn't support Thunderbolt.
It has Display Port over USB Alt mode.
A little more info on this: https://blog.startech.com/post/tech-talk-using-usb-c-and-displayport-over-alt-mode/
Could you try and use your SP4 pen on your SB2 and see if it works like on your SP4, please?
I have an option to buy an SP4 pen for my SB2 and would like to know if it's working like intented (minus tilt and additional pressure points offcourse)
You could try and install the Intel Extreme Tuning Utility.
See these YouTube movies for more information:
youtube surface book 2 throttle - Google Search