I agree with this statement. Despite our attempts to develop various solutions, we haven't found a good way to enable multiple graders to assess assignments. Our University requires the 'four eyes principle', which means that at least two teachers must grade each assignment. We are still looking for an effective method to achieve this.
We also want, just for the objectivity, that our teachers can not see each other's grading and feedback. When they both graded, there should be a moment in which two teachers can see the feedback from the other teacher and discuss the differences.
After a compromise, they should be able to release the grade.