In terms of user content this would be correct. However when it comes to games on the platform valve does do curation to ensure games run etc. I don’t know if it has been tested, but that curation could exclude them from the protection. If that was the case they could be directly sued for copyright infringement.

I don’t know, but it might be that Reddit is only limiting API keys for authenticated sessions. That way the anonymous requests still work up to the free API rate limits.