Good thing I kept reading the posts. I was going to post my input that is JUST AS YOU POSTED. From my experience, modern GM vehicles have TWO timing tables (High & Low Octane). The usage depends on detonation. From the first start of the engine, the ECM/PCM selects higher of the two. If no knock (pre-detonation) is detected, that table is continually used. However, if knock is detected, the ECM/PCM selects the Low Octane table to use for ignition timing. This is known as Knock Retard. This is done without a driver's input so to optimize fuel burning (along with a slew of other things). I'll try to remember to post a screenshot of my HPTuners software that shows the two different tables.
I know, I know... that's a GM experience, but I'm sure Honda's very similar (if not the same).
