OOOH! OOOH!
there was a disclaimer at the end of the movie about the work at the pyramids.
i have the feeling they got money from the Mexican government to film educational movies about Nahuatl myths —hence the really high quality of the historical 'footage'. the clothing, jewelry, makeup are really close to what i have seen in actual 15th century Nahuatl codices.
so they probably shot those, completed the assignment, and with whatever was left they made this movie.