Thanks for the reminder on how to do that, and for why this is always confusing.
Yes the "OS Build" is 6.0 and the "Software" is 5.1. Apple has had this dual-numbering scheme for a long time and it is confusing -- I think the only time they've been the same for ATV was with the 4.3 release.
Is it technically correct to call this release "iOS 6"? I suppose, and you can call it whatever you want but all of the reviews on this release (and Apple's own article above) refer to it as "Software Update 5.1". Why Apple continues this dual-numbering is beyond me, but if you want to call it "6.0" then I won't call you a liar