What would be the purpose of the clause "not exceeding 15 minutes" then? The rule is clear: the competition can choose an inverval duration between 0-15 minutes

What would be the purpose of the clause "not exceeding 15 minutes" then? The rule is clear: the competition can choose an inverval duration between 0-15 minutes, the referee can alter it inside that range (I've only ever seen it extended beyond that span for unplanned force majeure reasons like a storm). In any case it's clear that the WC referee had no role in the scheduling of those half-time antics.