No point posting here Ark anyway, no official reads or responds to these forums.
But as to your deploying in center question, scenario 2 Ambush scenario has different wording on deploying. The defender starts deployed and like in most scenario's the attacker moves onto the table, sorry don't have scenario book with me to get exact quote. I don't know the Descent scenario, is the deployment described differently in that to? If not then it will follow the normal 'come on table' deployment rules, guessing by the scenario title these troops are air-dropped? If so then normal deployment rules make sense.