Tomato tomato
VR is for replacing reality, AR is for putting (useful?) digital things on top of the real world.
And VR with passthrough is AR unless you're being pedantic.
It isn't. It doesn't do what AR does. It's just an ease of use of feature. IUf you watch a security camera through a VR HMD is it AR? No, because none of the virtual world is being cast into the real world. It doesn't meet the basic requirements of being AR.
There are different AR implementations possible with different tradeoffs.