My question would be did you provide the welder with instructions on what was and what was not acceptable on the test?
I've said it before and I'll say it again, when a welder takes a test with me they are provided with written instructions of what they can and can't do, what tools are acceptable for preparation and interpass cleaning, what hold points must be observed (for in-process inspection), and the acceptance criteria that will be used to assess the test piece. Before they strike their first arc, I read it with them, ask if there are any questions, and then they sign it and keep it in their booth with the written WPS. All the paperwork is handed in with the test piece at the conclusion of the test.
It is unfair to change the game rules half way through the test. Neither AWS D1.1 nor ASME Section IX address grinding for interpass cleaning or dressing the welds once the weld is complete. There is nothing wrong with limiting the amount of grinding as long as the welder is informed of the limitations before the test starts. Likewise, if there is a need to limit the width of a weld pass because of limitations imposed by the code or due to company policy, it should be clearly stated before the test starts.
Best regards - Al