I can vouch for that. Amazon's own delivery system is not all that great. When they do deliver, that's fine. But when they don't, not the best feeling I tell you.
One time I ordered a couple of items from Amazon. Had I ordered elsewhere if they offered it, I'd get the shipping email 1-2 days after I ordered. Not with Amazon. For two items, it took them 4 days to get a shipping notification email. And it took them another few days for the order to arrive. Yet all this time, I had no way of tracking it unless I explicitly log into Amazon's site to get the full-blown detailed info on that tracking number. They did deliver my order as expected. But I do not like not being able to track a package w/o having to log in to get all the details.
Unrelated but definitely a part of Amazon's shipping system, I ordered a particular item and the store used and shipped out half of my order using a 3rd-party retailer that utilizes Amazon's "fulfillment service". The tracking number was formatted exactly like Amazon's and there was virtually no way of tracking it. The link I received via email tells me that it was never delivered. Yet whatever crap Amazon's "fulfillment service" is using to ship and deliver, they claim that it was delivered. Utter BS I tell you. I finally got everything delivered... but only because I was being patient with the store and had them ship another one out to me. I'm miffed that I had to go through all that.