If you set up a campaign to request seller feedback for your MFN orders, we wouldn't be able to receive any tracking information for these orders as there are too many different couriers.
So what FeedbackExpress will do is take the latest estimated delivery date provided by Amazon.
For example if the order was received on the 4th of the month, Amazon could send an estimated delivery time of the 7th - 14th of the month.
So in this case the delivery date we would use is the 14th.
If you set your campaign to send a feedback request as soon as the order is delivered it could happen that the customer gets an email before the order is being delivered (if there are any delays with shipping).
What we would normally advise for MFN orders is set up your Campaign to send a Feedback Request 2-3 days after the order is delivered, that way it will compensate if there are any delays with shipping.
For your FBA items, we will receive the tracking number so this situation cannot happen.