There have been a number of posts regarding the the need to ensure that the mitre slot is parallel with the blade on a table saw. Indeed it is highly desirable to do this to stop burning and to keep the kerf to a minimum in a partial cut, but it does not have any influence on the angle of the cut. The only aspect this affects the angle of the cut is the relationship between the miter fence and the mitre slot. Even if the miter slot was say 10 degrees out from the blade, as long as the mitre fence is at 90 degrees to the mitre slot in the table, the cut will still be at 90 degrees. You probably know this its just that a couple of members were having trouble achieving 90 degree cuts and were spending time trying to adjust the table top to eliminate the error.