The restriction اللفظ العربي identifies the linguistic corpus and technical framework of this discipline. It does not imply that other languages have no context-sensitive rhetoric.
Classical Arabic maʿani was developed through Arabic grammar, linguistic categories and examples. Its distinctions are therefore best assessed through the Arabic wording, its available constructions and the surrounding context.
A translation may convey the main message but miss subtle changes in fronting, omission or reinforcement.