Eh? Yeah, I know that about navies, hence why I stated that terran design focuses more on putting guns on the sides. Shivans tend to go sheer offensive, though, moving in and decimating anything thats in their way. Off the top of my head, I can't think of any time when the shivans were on pure defensive, where having good coverage would help a lot more. Also, when your on the attack, you tend to be moving forwards, with your front towards the enemy.
As per the Sathanas backside thing, wouldn't work. While they turn obscenely slow, they can still make it in time to slag any ship attacking their rear before they're even at half health.