haha, well, i dont know **** about s4's...it doesnt look stock, but it looks too 'good' to be hood, haha.
ive tried to avoid abs in my driving career, so far 2 for 4 haha, but most ive seen have been straight hard lines all the way, like you said. id be skeptical about that too, but if its stock, i guess its not so bad, haha.
the silver retaining plate attached to the firewall is a giveaway that rubber lines go into it...
plus its vw product, so dont use regular logic whats weird is that the main line and return line seem to be rubbing freely on the one "wheel" line
but, yeah, if you remember the accord's fuel line under the hood, it was a hard line from the fuel rail "back," where it became a rubber line with one of those compression fittings making the connection.
i'm guessing the stainless is acting like the flex pipe on your exhaust...it will flex, but only to a certain point without cracking/rupturing (like if you needed to lift the pump to access something in its vicinity).
or abrasion resistance if there's a hood brace that sits right between the washer fluid and coolant reservoirs?