وَقَدْ يُطْلَقُ الْمَجَازُ عَلَى كَلِمَةٍ تَغَيَّرَ حُكْمُ إِعْرَابِهَا
Majāz may also be applied to a word whose grammatical case ruling has changed.
A case ruling is a word's syntactic status and the nominative, accusative, or genitive form resulting from that status. Deleting one element or adding another may change the governing relation of a surviving word and thus its grammatical case.
The issue is not merely a different final vowel heard in isolation. The change follows from a different syntactic relationship. Comparing an underlying construction with the expressed construction reveals what has changed and why.