Thinking about it, I wonder if that is what the "conversion guide" is about: they had a design goal of making it so that there was a one-to-one equivalent for each 2014 Monster stat block by name (am admirable goal).
But that goal is not compatible with that bit you quote here: so for former Humanoid stat blocks, say the Orc, Oregon, or Drow Priestess of Llolth...maybe they have been renamed and repurposed, with the conversion guide explaining the new equivalent.
the only formerly Humanoid Monster blocks we know of specifically are the Kobold/Gnoll/Hobgoblin/Goblin/Bugbear Warriors and the Kuo Toa...and we know those have all changed Creature Types, unlike Orcs or Drow.