Why does that Apple support page say "Late 2013" for the Mac Pro? Was there an "Early 2013" Mac Pro that they don't want you to get confused with?? Why not just say "2013"?
that's the first place I've seen apple discuss how the buses map to the hdmi and tb2 ports.
Because every other Mac has a Early/Mid/Late adjective next to it. It is a consistent practice. There are typically not multiple releases per year for most of the Mac line up in any given year.
...I could understand naming one an "Early" or "Mid", given that there is a slight chance a second model would be forthcoming at same year.
There is no reason on earth to ever name a "Late" model in a one-model year since there is zero chance of a later model being released.