This is consistent with what customer service and an several in-store sales representatives from our area's highest volume store said as well.
I don't like it anymore than anyone else, but, this seems to be the case. I will only believe earlier shipping than what TMO is consistently stating until I see it 1) on my order, or 2) someone posts a full capture of their earlier tracking information (including package weight, and obviously with personal information and tracking number redacted).
Also, on the topic, I have had scheduled deliveries in the past for both UPS and FedEx where the scheduled delivery date was confirmed (or so I thought) then got pushed back one day after another. These were not phone orders.