This is very poor advice to give to people when you don't even know there skill level because depending on the system you are working this is not always the case.
A true statement is that you will never get shocked if you are at the same potential as the voltage you are working on.
I am curious as to were you served your apprenticeship...I served mine in Wisconsin and here it is a code violation to tie the grounded conductor to ground other then in a main panel or a separately derived system such as a transformer although I believe this is the case nation wide...
So the white wire is NEVER terminated on the grounding screw other then stated above this can lead to an electrocution hazard.
We should also clear up the nomenclature
Black wire = "hot" or Ungrounded conductor
White wire = "neutral* or common*" or Grounded conductor
Green wire = Grounding conductor
* Note: there is a difference between the term common and neutral but in this case it doesn't matter...