He either changed his mind, or he didn't want to totally spoil us..
I haven't reread Christmas Eve at the back of Battle Ground yet, but when I read that he had been kicked out of the Council, that got my attention too. What I thought was either at some point before Christmas he got reinstated, or even if he no longer is a member of the White Council, he still sees himself that way.
Also did you catch in Battle Ground just after he is kicked out and Michael finds out and swears loudly enough to make a sailor blush, he tells Harry that Charity has invited him and little Maggie
over for Christmas Eve because she knows it will be painful for him without Murphy.
But face it, except for that little spoiler that he changed, most of us figured out from the tone of
it that Murphy had been killed in the battle.