"A decision rule that works in one context can fail disastrously in another.
A standard is not a moral statement. In a system boundary decision that affects two teams, it is an agreement about what the system will do under pressure. Without that agreement, you get exceptions by persuasion instead of principle.
In a system boundary decision that affects two teams, the fastest path is to skip the uncomfortable conversation. That buys speed today and inconsistency tomorrow. Name what you are refusing to optimize, so future changes do not quietly destroy the property you thought you were protecting. Make the boundary explicit enough that a peer could disagree with it; if no one can disagree, no one can defend it under pressure.
Herbert A. Simon is useful here because it forces precision. Surface the assumption the plan depends on and name the first signal that would prove it wrong. Do not add ceremony; add precision.