They show horses equipped with modern day tack. Adjustable head gear with polished brass and chromed rein tips and buckles. More likely in 350 BC they had knotted rope type harnesses
There's an anachronism when Alexander says they must move-on and "turn the page". But books with pages weren't invented for another two hundred years - about the time of Julius Caesar. In Alexander's time they rolled up paper in long scrolls.