Ibarat al-nass conveys the meaning directly intended by the discourse. Isharat al-nass conveys a necessary implication of the wording that is not its primary purpose. Both may arise from one verse, but through different routes.
وَعَلَى الْمَوْلُودِ لَهُ رِزْقُهُنَّ وَكِسْوَتُهُنَّ
The father is responsible for their provision and clothing.
Maintenance is expressed directly, while the wording also implies a point about paternity. An isharah must arise from the text, not from speculation.