A former girlfriend could smell sulfite at levels far lower than anyone else in our AWS group could, so folks can be very sensitive to different things.
Also, reading a hydrometer includes judgment on the part of the reader, e.g., most are graduated at 0.002 increments, so the exact reading (unless right on a line) is a judgment call. I admit that I only take a careful hydrometer reading at 2 points -- initial and bottling. In between, if the reading is off by 0.002 it doesn't make any significant difference. It may be that the reading does not appear to change while the last drab of sugar gets eaten.