I just finished a 25 year Dynasty...none of my players Jerseys were retired but then again I didn't have any players that were real superstars. Anyway...at the end there was no letter grade screen...just access to GM History, Team Records and Team Stats. That means that the "GM Evaluation" option means something else. To me it sounds more like it's giving you the option of choosing to be judged and thus fired...and by turning it off you can stop teams from firing you.
Also...I just noticed that when simming my first year of franchise Paul Pierce averaged 30 points per...the second year he's now averaging 18...I think the comp only has D-stats for the first season then goes completely from ratings after that.
PS: If you set it to simulate a certain number of games...you can stop it midstream now...which is very useful.