A targeted order is one thing, but this applies to ALL data. My data is not possible evidence as part of a lawsuit, unless you know something I don't know.
The government's power to compel private companies to preserve citizens' communications needs clear limits. When the law is ambiguous about these boundaries, courts end up making policy decisions that should come from Congress. We need legislative clarity that defines exactly when and how government can access private digital communications, not case-by-case judicial expansion of government power.
Their point is that the discovery is asking for data of unrelated users. Necessarily so unless the claim is that all users who delete their chats are infringing.
Your point illustrates exactly why the tension between due process and privacy rights can't be fairly resolved by courts alone, since they have an inherent bias toward preserving their own discovery powers.
