Originally Posted by Jodou
So after some extensive testing, I can conclude that: we're both right. Modern Warfare 3, for example would indeed cancel out other platforms if I marked even one of them not interested. However, when the new Oblivion anniversary games showed up in my recs, I was able to remove both PS3 and 360 without losing my recommendation for PC. Furthermore, it showed up in my quick picks immediately after. I will revise the OP to reflect that there is no longer safety in marking just one not interested and that you will need to test it yourself before removing recs.
I figured out what's going on, though I obviously can't explain why Amazon is doing it. Multiplatform games (or games with collector's editions) that Amazon allows to be selected from within the product page are the ones that get swept together when rated/checked off; multiplatform games that have individual product pages (of which I can't find many) can be rated/checked off without affecting the other platform SKUs.
Resident Evil: Raccoon City Operation
If you notice on the product page, you can select which platform you want. For whatever reason, games with that type of product page are the ones that are getting lumped together, in spite of their unique ASIN numbers.
Contrast that with:
Oblivion 5th Anniversary Ed.
You'll notice you can't select which platform you want from within the page, despite the fact that the Oblivion is obviously a multiplatform game. Because of that, if you indicate you're not interested in the 360 version, you'll still get the PS3/PC versions in your recommendations/quick picks.
Why Amazon changed the way they do things is beyond me, but at least we know which games we can now safely rate/check off without impacting the other SKUs.