Fitting an S-Line diffuser on ´06 Sportback with S-Line exterior?

[Tracebuzta]

As usual, Audi Denmark don´t know anything about the cars they sell

I have the standard diffuser? - Can I fit an S-Line diffusor, for example this one?
Audi A3 S-line Diffusor Heck-Spoiler 8P0 807 521 K NEU | eBay

Audi tells me that it can´t be done on my car