It turns out, in this particular case, the reason the rotating beacon was left on during the day time and was NOTAMed as such is because it was broken and could not be turned off by the tower.
What has been gathered is that there is no standard reason why an airport would intentionally leave its rotating beacon on during the day in VMC conditions.
FICON is outlined in FAA JO 7930.107 "FICON REPORTING".
FICON is the "FIeld CONditions reporting. It identifies information that used to be called "braking action", but is now a little more succinct.
The conditions for the runway are reported in thirds, [First Third]/[Middle Third]/[Last Third], with the following data outlined on page 6:
So 5/5/5 means ...