I think one of the reasons they wont show the results is because of conflicts in the past. Once you passed you passed and that shall be it.
Ex. X company had 2 candidates that qualify as a senior engineer promotion. But they both needs to get their PE first. Both candidates took the test at the same time. Both passed the test, but, one with score of 70 and the other with score of 95. Then there comes the conflict...does the one that score 95 a better option?
Thats one of many reasons they dont show scores any more.