I've never heard that supposed "disagreement".
Yes, there is differing opinion on when to start the Christmas music, but in general from week #1 the audience size increases with additional TSL and cume.
Running the regular format on a stream or on an HD channel is simply a promotion that enhances image. The streams don't produce revenue or marketable ratings.
The Phoenix station that did the first full-season Holiday music got immediate high ratings and no significant complaints. In fact, what Jerry Ryan, the manager, noted was that the post-Christmas listening in the Winter book was higher than previous Winter books, indicating that the Holiday format had brought some new listeners to the station, permanently.
Obviously, you are prejudiced and are bringing your distaste to the discussion. You call the music "Christmas Muzak" yet the seasonal format is quite well researched to play the songs that the AC core and other potential listeners most like.
To begin with, AC is a predominantly female format, so we have to look at how the format is incorporated into the lives of the listeners. Just as many don't understand or like the Hallmark channel Christmas movies, the focus of both Christmas radio and that TV service is on a particular lifestyle... and should be respected as even in highly ethnic markets like LA, the Christmas music station may cume as high as a third or more of all listeners (and even more in the target demo).