I agree. The Pracinha was the UU for them in Civ 5, however they probably wanted to differentiate them this game. Although I would also argue that the Voluntarios de Patria would be a more ideal gunpowder unit, in my opinion, especially if Pedro II continues to lead Brazil.For me personally, only the Pracinha could potentially replace the Minas Gerae, and even then, it's not by that much.
And it's not like there's an iconic UU such as Japanese Samurai, or Persian Immortals, that would make the Minas Geraes or Prachina show up every game. They can easily switch them between versions.