The phrase فَكَأَنَّمَا قَامَ نِصْفَ اللَّيْلِ emphasizes the exceptional merit of congregational ʿIshāʾ. وَمَنْ صَلَّى الصُّبْحَ then presents an even broader comparison for congregational Fajr.
“As though they prayed the entire night” is a comparison of reward, not a claim that the individual literally remained awake all night. Merit associated with one good act never makes other duties unnecessary.
A practical application is to arrange work, rest, and waking hours so obligatory prayer and consistent worship are not neglected.