The Surface devices seem to use MAX34407 (up to Pro 6) and MAX34417 (later) to measure power consumption for various components / part of the system (see e.g. https://github.com/linux-surface/acpidumps/blob/master/surface_book_2/dsdt.dsl#L18219-L18226).
Datasheets:
The missing drivers don't impact system performance, so this is a low priority issue.