In fact the carrier is said to be testing variants of the phone. According to @evleaks, “AT&T already testing both Galaxy S7 variants (SM-G930A and -G935A), adding weight to rumors of an early- to mid-1Q16 release.” Last we heard, there could be more than one version of the Galaxy S7, there might be three versions in fact.
One version is supposedly a Qualcomm Snapdragon 820 phone, the other is an Exynos 8-series handset, and the other is the Exynos 7422-powered Galaxy S7 which is supposedly aimed towards the Indian market. In the case of this particular rumor, we might be looking at AT&T testing the Galaxy S7 and the Galaxy S7 Edge variants instead.
Rumors of the Galaxy S7 are going a bit wild at this point. We have heard reports of multiple variants, and just recently there was talk about a possible Galaxy S7 with a 4K display. In any case take it with a grain of salt for now, but hopefully we will have more details about the upcoming handsets in the near future.