The answer is in full per the Q and A [bet it's not in the new rule book either -- opportunity missed].
Mark posted on Facebook
Hi All, I spoke to a couple of friends about the raise dead issue we talked about. There has been a Q&A which I missed that now makes that move illegal as it turns the combat onto 2 fights. The raise dead have to go in the flank and can't go on the rear if your charging a 2 rank enemy. The way I think I will remember it is to ensure 1 of my raise dead stands is touching one of my normal stands. Hope that helps
What the WMR Q & A it says
Raise Dead - Q - Are there any other restrictions in placing a raised unit of skeletons into combat?
A - Actually there is one. A raised unit cannot be placed so that it would split a combat into two separate engagements. This typically happens when a unit of infantry supported by another unit from behind is charged by a undead unit to the front and a new unit is raised so it only touches the supporting enemy unit.