Some of the ships in Lead by Example have unusual firing arcs.

The MC80A has turbolaser batteries on the aft, but they apparently do not fire into the Aft arc. Additionally, the ion cannon batteries all have "Forward, Port, and Starboard" regardless of where they are mounted (this latter issue also applies to the Munificient's light laser cannons which have "All" regardless of where they are mounted).

The above could be simple errors, but the next few are where it gets weird.

The Surveyor has "All Dorsal or All Ventral" along with "All Port or All Starboard" listed for its weapons. While the former makes some sense, the latter doesn't really mesh with what we've seen on firing arc so far. The "All Port or All Starboard" shows up again with the Munificient's light turbolasers.

All Dorsal/Ventral/Port/Starboard would be "the weapon is mounted on the Dorsal/Ventral/Port/Starboard side and cannot fire into the opposing side"

So an "All Dorsal" would be top mounted and could fire into Fore, Aft, Port, and Starboard arcs as long as the narrative didn't have the attack coming from below.

Being the combat book, I think they are expanding the tactical aspect of space combat.

I said I could see some merit in All Dorsal/All Ventral, but what about All Port/All Starboard?

All port/starboard would be Fore, Aft, Port or Starboard but not anything in Starboard/Port.

Basically if you would have to fire through the ship, you can't hit it. In some of the other books you see firing arcs of "Aft, Fore, and Port" for weapons that are specifically mentioned as on one side of the ship. I think this may just be another way of saying that and beginning to add Ventral/Dorsal arcs.

I'm not sure what advantage saying "All Port" would have over just continuing to say "Forward, Port, and Aft" especially as several of the ships in LbE still stick to this established method.

Also, you mentioned "Being the combat book, I think they are expanding the tactical aspect of space combat" and I forgot comment on it. Having looked through LbE, there is almost nothing in it regarding actually using ships in combat (as opposed to the mass combat rules where firing arcs and other tactical elements mean almost nothing.

They've been doing that a lot lately. Like the Interceptor-IV frigate though there it was the firing arc being too restrictive not too loose. If the Int-IVs turbolasers could fire into the Fore and Aft arcs sure it would still be massively undergunned compared to its depiction in FOC and to the weapon loadout given for the Interceptor-I class in legends but it would at least be able to ave somewhat of a chance against combat ships its own size. As it is pretty much anything Sil 5 or up armed and not an armed freighter or a purely anti-fighter ship will eat a Int-IV for lunch because it A: only has three weapons, and B: there is no way to concentrate the fire of those weapons because each of them can only fire into a single arc.