Spark advance massively retarded after cleaning MAF sensor and throttle body

The title of the question is relatively self-explanatory. I just cleaned my MAF sensor and throttle body (electronic); the weather is warm again and I don’t think either of them have ever been touched in the 103,000-some miles this car, a 2002 Maxima, has accrued. After cleaning and re-installation, I performed the necessary throttle valve position relearn procedures per the service manual and went on my way; and the car runs fine – better than ever, in fact. Idle is still a little high, sitting at around 850 RPM rather than the usual 660, but I’m sure that’ll go away as the computer relearns what it needs to on its own.

However, while I had my scanner plugged in after a short test drive, I noticed something strange: the spark advance value which, before the cleaning had typically hovered around 14°-16° degrees at idle (engine fully warmed up), was now hovering at around 3°-5° degrees (again, engine at operating temperature).

Thus, my question: why would this occur, and could it be indicative of another issue or set of issues?