Even with my wiper in the off position, every time I start the car, it seems to move slightly. Like a wiggle.
Is that normal?

Yep.

I believe the design is to prevent the wipers from frozen in winter.

Its normal, mine does it too.

I never noticed that in mine. Which year/model does that?

Nothing to do with detaching in winter. If they are frozen, they wont move (atleast where I live). You always have to detach them manually before using.

Owners Manual:

Front wiper and headlight washer system
0 – Windshield wipers off
When the windshield wipers are switched off, the wipers move up slightly from their rest position so that the wiping edges are aligned correctly.

Ok, but that's what I was told by the salesman.

You really believe what your salesman says?

When the BMW E60 M5 came, the salesman argued with me that the car didnt have launch control(Wrong!). At Audi, the salesman said that you cant have electrical wiring from the Webasto fuel warmer to a engine block warmer plug installed in the bumper of the car. This allows you to actually reload your car battery, while it stands in the garage or an outside electric plug, during the cold months we have here. (Wrong!) I can go on about stories of similar insidences...

In my car the wipers dont move, except when I turn them to the off position. No movement when I start the engine.

Mine moves slightly also (2010 PTT).

My 2013 GTS does this also.