So we invert it. A catalog brief has required fields, and we either accept it or come back with one consolidated question. Not a thread. The turnaround clock starts at acceptance, which gives both sides an incentive to get the brief right the first time.
Agencies sometimes read this as bureaucratic. It is the opposite: it is the only way to publish a turnaround honestly. A vendor who starts work on a vague brief is not being accommodating, they are moving the delay to the revision stage where it costs more.
The side effect is that briefs improve. After three or four orders, partners write them tighter, and delivery gets faster for reasons that have nothing to do with us working harder.