What does that link represent? Isn't it just a declaration that they have patents which may conflict with Opus? Isn't that just what a patent holder is expected to do?

It represents their nastiness. They were contacted and it was explained to them how their claim is invalid and those patents don't apply to Opus. But they refused to remove this claim, "just because" (may be they like creating FUD). You can ask Opus developers for more details on this. Qualcomm acted out of bad will here.

Most non-troll patent holders only use their patents defensively.