Just like when Hitler let Allied troops be extracted from Dunkirk.
I just love how the media is uncritically repeating Nazi talking points. And this is the same soldier that the MSM has been showing giving updates on Mariupol. Note how he has the Azov patch on his chest covered. Previously he'd had it out in the open. Of course its all moot when there's another soldier right next to him proudly wearing their Azov patch on their sleeve.
There already is an extraction procedure: You walk out, slowly, unarmed and with your hands above your head while saying "I surrender"
But then you take away from the poor wittle nazi defenders what nazis love the most: murder-suiciding their wives and children instead of surrendering to the approaching Russians.