If you are flying at 35000ft then you should be flying at a flight level of 35 with all the other a/c in the area flying on 1013.25. minus 10 degrees is irrelevent. I agree with all using the same datum, however radar cannot determine the datum a/c are flying to. It is easier for the controller to have all the a/c flying on the same pressure setting to ensure separation.
Please keep safety first.