I have seen the instructions, because they came with my official MoparOnline rear spoiler (and stronger springs), which I ordered from and recently picked up at my local Alfa dealer. I "negotiated" a price that's higher than what's shown on the Mopar website, but I'm sure the local asking price included shipping and store profit. Both the parts guy and I are OK, and these are the guys that've very satisfactorily serviced our two Italian cars for over seven years.
Not in a rush, but I can tell you the official Alfa Romeo factory spoiler I received is the genuine article. It's not fiberglass and it's not carbon fiber. It's plastic, hollow, primer gray, and is imprinted with the European the factory codes and diagrams that can only be molded in plastic of some sort, and yes, it does have the two mating holes to line up on the decklid of a QV. It also includes paper templates to tape on both sides of the trunk lid to properly line it up if it's not being installed on a QV. The written instructions are comically brief — all pictograms; no words, though the disclaimers are printed in 17 languages.
There's a thin (maybe quarter of an inch) strip of 3M super tape all the way around the spoiler already installed. There's also a continuous, thin (maybe an eighth of an inch) indentation that runs all around (maybe half an inch) inside the tape outline. The pictogram shows an ordinary caulking gun applying a 3mm bead of an unnamed "adhesive" into the indentation. And nothing else! End of pictogram! Before I turn mine over to someone trustworthy and experienced to install, there will be a discussion about what version of liquid nails -type adhesive to use, among other parameters.
But I'm quite certain the spoiler I chose, being the real deal, and appearing to hug the contours of the decklid more closely than the other spoilers I've seen on the forum, or seen available online, my worries about water freezing and separating the spoiler inside the gap will be assuaged. Photos will follow, but "social distancing" and cold weather have been slowing my progress. I'll be getting mine painted in simple gloss back, to coordinate with the black window trim, the gloss black sunroof areas and the flat black (mostly in shadows) lower rear "extractor".