This is a special "launch varient" thing. The same thing occured with the A7.
The Prestige's included LED headlights (not advertised) even though they did not have Innovation or LED package. If you find one on a dealer lot like this, you luck out.
If you're ordering, you need to pay for them otherwise your Prestige will come with Xenon's (as advertised). If you ordered very early on (first production pull) you also lucked out and got them free if you didnt pay for them and got a Prestige.
All the new A7's hitting the dealers now that are Prestige are coming with the advertised Xenon's. The first allocations they got all had LED's on Prestige regardless of Innovation/LED pkg's. I'll eat my hat if the A6 isnt the same deal.
Edit: To add, the special "launch" cars that had this will have a line on the window sticker option list that says "CORPORATE" with a $0 charge.