These are available for s lines on eBay. I was very close to buying one myself maybe from a different seller mindIrrespective of whether you like it or not, why would this not fit a Sline or RS4?
I understand what you are saying. It won't fit rs4 because the wings are further out, but I agree it should s line as it's the full bumper and not just the grill, although having said that are the air ducts different?..
the problem is made worse by sellers stating fitment such as " wont fit s-line s4 rs4 " which does'nt apply in many cases , and certainly not with bumpers.
if you search ebay for an RS4 oem grille for example , if i enter my own car reg or specific model details into the search it will come back as " this item will not fit or does not fit " your model, but we know thats rubbish because we fit them without issues, becuase that part will fit accross the a4 B7 platform with the s-line format bumper, the same applies to most parts of the front bumper fittings, many parts will fit accross differening models due to the basic format of the bumper.