It is in the lore, however. Every single time you see a Klingon Bird of Prey in the shows or movies, they are always facing their targets. They don’t have the ability to fire behind them. It is a basic thing. Cannons are directional with a possible 45-90 degree firing arc, banks and arrays can be omni-directional with 180-360 degrees.
You are absolutely correct, it is in the many years of lore both fan-made and official. That said, that wasn’t the point I was making, I was referring to STA not having combat/conflicts set-up with the degree of “realism” you seem to be seeking. As the mechanics of STA stand, from my understanding, they are not designed with specific mechanics relating to firing arcs (port/starboard/fore/aft/ventral/dorsal). I’ve played many a game in which combat mechanics were set-up to be intensely “real”/“simulationist” and those in which it’s far looser. My preference are for those mechanics which allow for a more cinematic/story oriented approach - something which STA hits on nicely for me.
On the other hand, the cinematic approach appears to be insufficient for you, at least from what I gather from your responses. With a little work, you can easily tailor STA to your expectations. I would advise looking to the FASA Star Trek Starship Tactical Combat Simulator game for inspiration - ships had six different shield generators, firing arcs, rules for firing upon “detected” cloak vessels, tactical heading changes, power:movement ratio, power:shield ratio, and more.