Keep in mind that they are not always in that position. If that’s how they are synchronized, the when they’re both 90 degrees to that they will miss spots in the center if you go too fast.
I spent a considerable amount of time researching this after my zero-turn (Toro Timecutter) had the same issues with leaving grass uncut in the center of the mowed strip. I actually wrote a computer simulation of grass being cut with various blade configurations on mowers to better understand...