[UPDATED] Conflicting info on if T-Mobile iPhone 5S comes unlocked - Seems to be...

[Update 10/17/2013] She received the iPhone 5S as a gift today, loves it, and it is totally unlocked. The AT&T/Net10 NanoSIM worked perfectly with an "T-Mobile" "Contract Free" iPhone 5S purchased on the Apple Store.

[Original Post]

I purchased an iPhone 5S for my wife (her birthday is coming up) from Apple's online store. While I was purchasing it, it specifically said it was "unlocked" and the receipt I received (in email) reads as the line item:

iPhone 5s 16GB Space Gray (GSM) T-Mobile, Unlocked

Some folks on Twitter have said that they bought from T-Mobile directly and were able to use their AT&T SIM cards. Others are saying that the T-Mobile iPhone 5S is carrier locked and you will have to call them to unlock it. The iPhone 5S SIM card page (http://support.t-mobile.com/docs/DOC-9305) states something similar.

Does anyone know for sure? Given the fact that the receipt lists the phone I purchased as being "unlocked", I would assume that it is... I'm asking because I don't want to open it when I receive it and her birthday isn't until near the end of October. I'd like to know before then so I can return it if need be.

Thanks for input.

UPDATE 10/4/2013

I've received the iPhone and it appears (according to iphoneimei.info) that the SIM is unlocked. Because this is a birthday gift, I've kept the box seals in tact and have not verified 100% that it is an unlocked device. That being said, all the evidence is consistent with it being a totally unlocked iPhone 5S (GSM). Therefore, purchasing a "T-Mobile" iPhone 5S from the online Apple Store appears to yield an Unlocked iPhone 5S (GSM) with a pre-installed T-Mobile nano SIM. Below is my iPhone IMEI check image with S/N and IMEI number blacked out.

5wkkypb_medium

via i.imgur.com