Sure, but so is TMo's mid-band, which typically rates much faster (likely due to better infra/backhaul), in most places, but they're not calling it "T5G+", or something, eh?
Pretty much all the carriers have bandwidth in all 3, but ATT is the only one (that I'm aware of) that "markets it as if it's a different technology of some sort", it's just weird, and smarmy, but maybe that's just me (I'm a s/w and h/w engineering type, marketing is generally my nemesis, to some degree
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You're right, it was "5GE", good catch. I do recall someone getting after them for then, not sure if it was a govt agency for false advertising or similar, or a competitor...
I see 800 and 900 (Mbps) duplex in some places now with mid-band TMo, which seems like a ridiculous amount of data for a phone, for almost any use. mmWave was mostly a gimmick, perhaps useful for some really high-density stuff, but with it's (reportedly) terrible penetration of most walls and such, just how many Femtocells or similar are you going to need, say in a 500 room hotel, hmm...
VZW sort of hosed themselves on mmWave, IMHO, thinking they'd roll out a few cities, and market say 2Gbps speeds, in a few city blocks or something, and somehow sell 5G phones and the whole deal, even though 99.x% of their customers had zero way to access their rollout, for a LONG time.