I don't think your order has been grabbed by FDA. You said that the tracking info showed it released by US Customs and I think that's where it would have been grabbed by FDA. What I think you are more then likely experiencing, is the delay caused by Monday being Columbus day. I know many people (including myself) who have orders that seem to be taking longer to receive than normal. I had an order shipped to me last Friday the 8th. from a vender here in the USA that I usually receive shipments from in 2 days. That should have put my order here on Saturday. But Saturday has come and gone, as well as Monday and Tuesday. Today being Wednesday and still no package, this order is now 2 days late (from typical shipment time) even when I take into consideration the post office being closed on Monday. So I think this whole Columbus day is the real culprit here. Seems to me the post office, knowing that Monday was a legal holiday or national holiday, decided to stop doing anything last Friday.
As far as shipments from Greenhouseone, I've ordered from them before and had excellent service and delivery, especially considering it's coming all the way from China. Orders placed are typically shipped within 24 hours, and from the time of shipment in China, to me in Wisconsin, was only 5 days. Some U.S. vendors can't even duplicate that. LOL.