Chris
As John mentioned I think you have miss-understood.
We are not saying a grinder can not be used to remove excessive reinforcement.
What I meant to say is
At our Company
I am with any personnel when they are qualifying to weld in our shop.
First, they have shown me that they are capable of qualifying, they did this by running a 3f and 4f fillet weld break test either on applying or at lunchtime or after hours, if they are moving with in the company from say a welders helper to a welding position.
Second, they sign a document for me/my employer that lists the criteria of this testing. It is written to AWS D1.5 Qualification, that way I can document qualification to AWS D1.1 and D1.5, it also has an Ethics Statement.
Third, I oversee the qualification from start to finish grading the individual if you will as to what I can expect and or what they need in the way of improvements.
As to why I would reject a welders qualification if they ground the weld without my inspection is
In AWS D1.1-08 Clause 4.8.1.1 Visual Inspection Groove Welds (3) Weld reinforcement shall not exceed 1/8". The Weld Profile shall conform to Fig. 5.4 and shall have complete fusion.
Sorry for any confusion
Marshall