Why the surviving German fleet would retreat without seeking internment

Would the surviving German ships leave for foreign ports to be interned?

No. The scenario assumes withdrawal to German bases farther inside the Baltic so the remaining ships can still contest British or Russian access.

Internment would remove the surviving ships from the struggle for the Baltic. That would hand Britain and Russia an advantage Germany still has reason to contest. Moving the ships toward a foreign destination would also require passing hostile naval forces, including the Imperial Russian Navy. The proposed alternative is retreat to a German base such as Danzig, despite the longer response time that follows.