You _must_ do this for every account if you have multiple.

As I would expect? I don't know of any service that has a "And also do this for all my other distinct acounts too".

A global "turn off and delete all location history on this device" would be best, really.

At least for turning it off I expected it to be phone wide, not account specific. Deletion yeah, I suppose you're right.

It depends how you view what you're setting.

Do you think you're setting a behavior of the phone, or a behavior of your account?

I guess it could be both but I view it first as a setting of the account since you can also be location tracked perhaps by a browser, or your Wear device? That would be my first go-to on that setting but I guess it can be seen both ways.

Wear devices have to be paired with a phone and browsers don't really have the constant access they want for this.