I wonder if that's because people are using the years on compliance plates as the model year, as that's not all that accurate? A late '82 will be an SD along with an early '83 and so forth. So, a late '83 will be an SE...
For example, I know my GS450 is an EZ model, and the manufacturing date is 10/81, but it's most definitely not an EX ('81 model year).