Ruthless by Anne Mette Hancock

Hi! Has anyone here read this book? Have a question about the ending that I am so confused about.
How did Zollner not identify the body that they found at the boat fire as Jan Fischhof? I understand that it was Tom's boat and maybe that's why they assumed it was Tom's. But wasn't it obvious from the face or even done DNA tests and identified it as Jan's body?