The wording of it is a bit problematic, for sure. A "voluntary interview" may or may not come with the alternative of arrest. In this particular case, it did.

The wording of it is a bit problematic, for sure. A "voluntary interview" may or may not come with the alternative of arrest. In this particular case, it did. In some cases, it doesn't. A voluntary interview may also lead to arrest (eg: if you admit to a crime, they usually arrest you to charge you).