Roy,
You pose an interesting question! When I did my instrument training I
always filed under my instructors name (neither of my two instructors
ever commented on this).

So to add to your question, I'm now wondering:
I usually only file my last name, and have never received a single
question by the briefer about it. Do any of you know if you are
supposed to file first and last name? Also I had always assumed (as
mentioned by some of you) that the name only ever mattered if there was
an incident. Barring any incidents, do any of you know if ATC/FAA ever
even looks at the name on any flightplan? What if we all filed as
"Smith" one day to see if they pay attention.....

By the way, good luck on your checkride. I hope that you can work out
the issues with your new instructor. Maybe he/she doesn't realize that
they are doing things "differently"?
-Jamie