Your interpretation seems to be that if the car is ever in a "fully autonomous" state, then it's "fully autonomous". Thus if a "fully autonomous feature" is enabled (such as on the highway), that's full autonomy even if that feature is disabled automatically in other situations (such as in the city). Some people would interpret "fully autonomous" to mean end-to-end autonomy, sort of like enabling a "full encryption" feature on a chat application doesn't make chats on that application "fully encrypted".

[EDIT: Given the medium and proposition, the appropriate interpretation seems to be the narrower one.]