وَيَوْمَ تَقُومُ السَّاعَةُ يُقْسِمُ الْمُجْرِمُونَ مَا لَبِثُوا غَيْرَ سَاعَةٍ
When the Hour comes, the guilty will swear they stayed only an hour.
The two occurrences of sāʿah have the same word form but distinct referents: the eschatological Hour and a short span of time. Shared form coupled with different meaning produces the wordplay.
Replacing the second with “a short time” would clarify the duration but lose the shared wording. Do not misclassify this as a simple repetition of exactly the same meaning.