Does org.eclipse.jface.preference.FileFieldEditor.setFileExtensions(String[]) work only in file explorer?

I am allowing only *.exe files in my FileFieldEditor. It does work well in file explorer, but if I type in text field path with other file type, I get no error message (file exists). Is this correct behavior? If so, I have probably to check if string ends with ".exe", or is there some implemented functionality?

Thank you for any help!

package test.preferences;

//imports

public class RootPP extends FieldEditorPP implements IWorkbenchPP
{
  //code

  @Override
  protected void createFieldEditors()
  {
    // code
    
    // Web browser
    FileFieldEditor browserFE = new CustomFileFieldEditor(
        PConstants.P_BROWSER_INSTALL_PATH, 
        "Web browser", 
        getFieldEditorParent());
    browserFE.setChangeButtonText("Browse...");
    browserFE.setEmptyStringAllowed(true);
    browserFE.setFileExtensions(new String[]{"*.exe"});//allow only *.exe files
    
    addField(browserFE);
    
    //code
  }
  //code
  
}

and:

package test.preferences;

//imports

public class CustomFileFieldEditor extends FileFieldEditor
{
  private boolean isPathValid;
  
  public CustomFileFieldEditor(String name, String labelText, Composite parent)
  {
    //this(name, labelText, parent, true);
    init(name, labelText);
    //this.enforceAbsolute = enforceAbsolute;
    setErrorMessage(JFaceResources.getString("FileFieldEditor.errorMessage"));
    //$NON-NLS-1$
    //setChangeButtonText(JFaceResources.getString("openBrowse"));//$NON-NLS-1$
    //setValidateStrategy(validationStrategy);
    setValidateStrategy(VALIDATE_ON_KEY_STROKE);
    createControl(parent);
  }
  
  @Override
  protected boolean doCheckState() {
    //code
  }
  
  @Override
  protected boolean checkState()
  {
    //code
    
    if (isPathValid)
      clearErrorMessage();
    else
    {
      Display.getCurrent().timerExec(2000, () -> {
        if (!isPathValid && !getTextControl().isDisposed()) 
          showErrorMessage(errorMessage);
      });
    }
    return isPathValid;
  }
}