Thanks I finally found it just before coming back here too. Yep, you look exactly right. Thank you.
I wonder the reasoning behind this? The Band 30 support for AT&T creates an entirely different model for Apple to produce. Why do that? If you need to have Band 30, why not put it in all the phones? I wonder if there are some advantages to the components in the non-band 30 models that make them a better choice if not being used on AT&T? Or, does it save maybe $1.00 on the units that don't need the Band 30 support and when you're selling millions, $1.00 adds up?
Whatever the case, it's disappointing for those of us who were not decided on if we'd use it on AT&T or T-Mobile. Now I feel I need to either re-order an AT&T model for flexibility (full price and get them to unlock it with receipt), or commit 100 percent to T-Mobile.
I'd say they save a bit on the radio filters, components etc by not putting BAND 30 support for all phones since AT&T is the only carrier expected to need BAND30
With that said, keep in mind BAND 30 isn't used or widely used by AT&T yet, and when it's used it'll be to supplant bandwidth in dense areas.
For future-proofing, it is a nice to have but personally I wouldn't worry so much about specifically BAND 30 support