Because what you're claiming is that somehow, your experience is different than their standard business practice and what everyone else has experienced. I'll help you out with your timeline. Once the approval from ATF is obtained, SC then sends out your certified letter to your local LE. I think we can assume this will take anywhere from 2-7 days to reach your local LE. They will then give your local LE 7 business days from the time of receipt of the letter to respond. So, right there, you're already into it at least 2 extra wks. Then, they will ship your suppressor. Again, another 2-5 days in a best case scenario. So, as you will see, your claim of getting it in 3-4 days is pure hogwash.
SC is indeed making up their own rules. They don't have to wait for your ATF approval to notify local LE. They can do it simultaneously while ATF is approving your application so that the wait times overlap. This is what EVERY OTHER retailer does. And it doesn't matter that they are sending it via mail. The rules are the same. What one poster has already indicated is what I suspected--SC thinks it's better business practice to only send out the certified letters(which are also totally unnecessary and not required by law) once they have the ATF approval because, heaven forbid, they might waste a stamp on one that didn't get approved. My guess is that >95% of applications eventually get approved by ATF. Is it really good business practice to avoid wasting a stamp for less than 5% and tarnish your reputation online with the customer base and lose potential future business that far exceeds the money saved for a few stamps?