magento2: "Customer > Address > State/Province" in admin backend does not honour the "State is Required for" setting, is always required

the “State/Province” (attribute region_id) selectbox in “Customers > Customer > {edit} > Addresses” is always marked as “required” when the selected country has states - even when the option “State is Required for” in “Stores > Configuration > General > State Options” is not enabled for this country.

this prevents saving the customer.

Preconditions

1. CE 2.1.0

Steps to reproduce

1. in “Stores > Configuration > General > Country Options” enable a country that has regions/states, we’ll use “Switzerland” for the rest of the steps.
2. in “Stores > Configuration > General > State Options” ensure option “State is Required for” is not enabled for “Switzerland”
3. save, clear config cache
4. create or edit a customer, add or edit this customers address
5. select “Country: Switzerland”

Expected result

1. The “State/Province” selectbox is popuplated and not mandatory

Actual result

1. The “State/Province” selectbox is popuplated and marked as required