Mubālaghah intensifies a quality; classical discussions distinguish tablīgh, ighrāq and ghuluww. Ḥusn al-taʿlīl presents an imaginative, aesthetically apt cause, not necessarily a literal causal explanation.
Iḥtirās adds a qualification to prevent a likely unintended implication. The first device concerns imaginative causation; the second guards the reader from misunderstanding an earlier assertion.