To me, it makes no sense, that non-ingame DLCs such as Soundtracks, Artbooks require an OS. They can be used on any OS. The only issue, that I see, is downloading them via Steam. In that case, the game and its required operatingsystem(s) may restrict on which computers those non-ingame DLCs can be downloaded. --Chick'n'Duck (talk) 19:56, 16 September 2020 (UTC)
PCGamingWiki talk:Editing guide/Monetization
OS for non-software
It's because PCGW typically doesn't concern itself with listing those sorts of "DLCs".
While it isn't outright banned, it's not enforced nor required as it's not a "downloadable content" that pertains to the game itself -- it's a standalone purchase/package/content not reliant or connected to the game experience itself.
I see. Though Steam requires to own the game, which does not make them "standalone". Btw: Do you know a case, at that the DLC and the game had different OS?
> Though Steam requires to own the game, which does not make them "standalone".
For soundtracks, this isn't actually the case any longer since January, when Steam finally separated them from games.
None the less, the fact that Steam restricts e.g. the purchase of these sorts of non-DLC stuff to game owners only isn't something that concerns PCGW. From our perspective, DLC pertains to additional gameplay content itself.
The "standalone" nature comes from soundtracks/artworks/digital goodies/whatever not actually having an influence on the gameplay experience -- it doesn't matter whether they're present on the drive or not; the game remains unaffected by their presence or lack thereof.
> Btw: Do you know a case, at that the DLC and the game had different OS?
Depends on how you mean. Occasionally DLCs have only been released for a single OS in the past. Recently, for example, it was revealed that Commander Lilith & the Fight for Sanctuary and the Ultra HD Texture Pack for Borderlands 2 wouldn't be released for Linux (and possibly macOS).
This is even more apparent for games as a service titles such as Rocket League, if they eventually drops support for an OS or another.