[toomuchtodo]

Write access, in my opinion, is where you have enough control to remotely override life critical or physical control systems that could cause death and/or significant physical damage to infrastructure and related failsafe systems can be bypassed or their thresholds exceeded intentionally.

An Internet rando should not have the ability to disconnect your 700kva interconnect over the public internet. If you breach Tesla and can command enough vehicles to charge in a constrained area to overload local distributed infrastructure, failsafes should kick in and physically segregate loads from the local grid.

Disclaimer: This is only my opinion as an infosec practitioner having done some infosec/GRC consulting for investor owed and coop utilities for FERC compliance.