before albion at least pretended that the soldiers they sent were volunteers but now they send an entire army and attack the empire, at that point why pretend they aren't enemy combatant? just kill them all.
because Empire don't want to give ANY excuse for Albion to declare open war. should open war happen, that would give Albion justification for complete naval blockade and announce to the world that Empire have another enemy, thus Soviet(?) to the East would have more incentive to attack Empire too.
this is where Gantz "Legalese" came into play. "AIM your misfire!" therefore, should Albion throw a fit of their soldier being shoot at, Empire diplomat would have a defense by claiming it's a "misfire". thus, Empire couldn't be held accountable for any injuries that Albion suffered. since it's basically an "accident".
yes, Legalese is somewhat of a bullshit. but it's the same Legalese that allow Empire to bomb civillian at Arene without repercussion.