A permission whose infrequency works against scrutiny
Emergency broadcast authority is the permission to send a single message to an entire user base simultaneously, rather than to one recipient or a defined segment. Because it's used so rarely by design, the access controlling it is easy to leave unreviewed for long stretches — nobody notices a gap in a permission nobody has needed to exercise recently, in a way that's much harder to overlook for a permission exercised constantly and therefore under continuous, incidental observation.
The consequence of misuse is disproportionate to almost any other single action a system offers: a broadcast reaches everyone at once, with no scoping, and typically with no way to recall it once it's sent — there's no equivalent of quietly reverting a smaller, individually-scoped mistake.
Treating rarity as a reason for more scrutiny, not less
This combination of rare use, severe consequence, and easy oversight argues for deliberately more frequent, active review of this specific permission than its infrequent use might otherwise suggest — periodic confirmation that only the intended holders still have it, rather than assuming it's fine because nothing has gone wrong with it recently. Rarity of use is not evidence of safety here; it's exactly the condition under which a gap is most likely to go unnoticed.