Gonna be a bit pedantic here because I love dungeon meshi so minor details being off annoys me more than it should.
Elves are considered a type of human in the dungeon meshi universe, as are all non-beastman humanoids (traditional humans, elves, dwarfs, half-foots, ogres, Gnomes). Marcille would be using the term "tall-man" rather than "human" when saying she studied human anatomy.