The point is, battalions don't have faction keywords anymore - I'm looking at the Nighthaunt battalions as I type, no keywords. And in the core book, all I can find is "If a player's army includes the units needed to field a warscroll battalion, then the player can include the battalion as part of their army by paying the points cost for it as shown on its Pitched Battle profile." I suppose its listed under the Nighthaunt pitched battle profile, but as far as I can tell the rules themselves seem to let you mix and match as you want.
And yeah, that's the difference in the gravesite rules. In LoN, each gravesite has that ability so you use it once per site, giving you up to 4D3 healed wounds. In LoG, the rule reads "At the start of your turn, pick a friendly summonable unit within 9" of a gravesite" which you can then heal/resurrect for - no mention of being able to do this once per gravesite, it's just 'pick one unit at the start of your turn'. Again, I'm hoping that's a mistake, but it seems odd when they could have just copy pasted the wording from the LoN book.