Definitely not in my manual. Mine is dated (on the back cover) 05.2012.
What's your manual date?

I also have manual 05.212 and no mention of this in there.

I also tried out waggling my foot under the bumper of my 2013 when I got home today - no trunk release. Prestige/Innovation.

Don't wag. Place foot under the bumper, pull back, place it a second time. Slight pause between.

Then, shimmy to the left, shimmy to the right, then do the hokey pokey and you turn turn yourself around.

I don't know if it makes any difference but I have the rear lid to lock set to On in the MMI.

Thats weird mine is 05.2012 as well. Page 40 to be exact. For me if I just gently kick the air under the bumper (have to be standing about foot away it will work. Takes it about .5 to 1 second to activate. The best example would be if you were kicking a ball to a small puppy and not wanting to hurt it just roll it over to it. We just got a puppy so thats where the example is coming from (got her the same day as my Audi arrived..so yeah...that day was good. A new Audi AND a new puppy!)

Well, I should've been a bit more specific - I did read through the thread and initially tried the forward, back, pause, forward method first. No dice on that... Then I tried a couple variations on that and at different locations under the bumper, no dice. Not sure what I have the rear lid lock set to...

Strange that they put in the sensor but not the power option that we have in Europe. Could it be a liability issue? Aren't power trunks pretty usual on American cars?

The risk of getting a lawsuit controls everything here in "lawsuit happy we want everything with no compromises like we are 5 years old" america.
That's also why we don't get remote window controls. Some kid probably dropped his big mac out the window and reached for it right as his mom forgot he was in the car as she went shopping in Arizona heat and crushed him in the window with remote window control. Somehow that would be the car makers fault and not the user pushing the button here in america... (steps of my soapbox.)

The A7 has a power lid so I doubt it's a liability issue. More likely a cost, design or parts availability issue. The early 2013 A6 order guide showed it as an option but it disappeared when the pricing came out.

Just tried this tonight (I have a 2013 Prestige), and my car does have this feature. Seemed a bit inconsistent - or maybe I'm just not doing it right - but it's there. Very cool.

Yah, it doesn't always work on the first try. Maybe it likes a certain type of shoe. It works for my wife every time though. Go figure.