As-salamu alaykum
The Quran deals with the most pressing of matters; the protection of a woman's chastity within the society that she resides in and curtailing / abolishing unwarranted charges against chaste women (24:4-5).
If you re-read verses (24:6-7), it is already clear that for either spouse (male or female), their 4 testimonies with a fifth of invoking God's wrath would stand as sufficient defence against any punishment / retributions.
Verse 24:8 simply re-emphasises the edicts already firmly established in verses 24:6-7 and by doing so, the Quran once again stresses the importance of protecting a woman's integrity against baseless accusations. As this is the focus, the reiteration to include males is arguably unnecessary.
The phrase 'wayadra-u' is possibly better translated as "And it shall avert" arguably implying a confirmation of an earlier edict. The verb 'dara'a' means to drive off or avert.
I hope that helps, God willing
Joseph