It has always been:
Tendency = distance the LB and DBs are off the line
Aggressiveness = blitz/rout jumping frequency
From the FAQ
The set is the defensive formation. The tendency is what the defense is looking for or leaning towards -- pass or run. For example, if a heavy run tendency is chosen, then the defensive players are pulled up closer to the line of scrimmage to try and stop the run but potentially leaves the defense open to a big passing play. The style is the overall style of play for the defense -- the more aggressive this setting is, the more often the defense will blitz, jump passing routes for interceptions, etc. The more conservative the setting, the more likely the defense will hang back in coverage. The red zone settings work the same way, but are used when defending inside the 20.
If someone is playing a conservative passing game, they will eat up your always pass defense; while if you play always run, a speedy WR will run right by the DB.