I agree, and said it earlier in this thread.
Confirmation Number
Why not nip the problem in the bud?
If the buyer has paid and has not received a shipment confirmation number in X days (I'm thinking 7-10 days max), then there's a problem and it should be dealt with.
Why focus on item arrival date, when this adds the extra variable of delivery method, not to mention the extra time the buyer waits before knowing something is wrong.
Again, I wasn't here when the rule was created, so maybe this is what the majority wants, but it seems like the metric is in the wrong place.
PS - I don't think it's just buyer apprehension with an unknown seller, OCD, etc. Some buyers want to receive what they purchase in a reasonable amount of time, regardless of how trustworthy the seller.