FP in S2755 when vulnerability is mitigated in another class

import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.ParserConfigurationException;

public class XxeA {
  public static DocumentBuilderFactory getDocumentBuilderFactory() {
    DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
    try {
      dbf.setFeature("http://xml.org/sax/features/external-general-entities", false);
      dbf.setFeature("http://xml.org/sax/features/external-parameter-entities", false);
    } catch (ParserConfigurationException ex) {
      throw new IllegalArgumentException();
    }
    return dbf;
  }
}

import java.io.File;
import java.io.IOException;
import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.ParserConfigurationException;
import org.xml.sax.SAXException;

public class XxeB {
  private DocumentBuilder foo() throws ParserConfigurationException, IOException, SAXException {
    DocumentBuilderFactory dbf = XxeA.getDocumentBuilderFactory();
    DocumentBuilder db = dbf.newDocumentBuilder(); // FP here, correctly secured.
    db.parse(new File(""));
    return db;
  }
}

  private DocumentBuilder foo() throws ParserConfigurationException, IOException, SAXException {
    DocumentBuilderFactory dbf = unkown();
    DocumentBuilder db = dbf.newDocumentBuilder();
    db.parse(new File(""));
    return db;
  }