There is no legal need for both; each procedure is legally valid. What is said in paragraphs 9 and 10 about a wedding talk and vows applies here too.
أَمَّا فِي مَا يَتَعَلَّقُ بِخِطَابِ ٱلْعُرْسِ وَٱلنُّذُورِ فَيَنْطَبِقُ فِي هذِهِ ٱلْحَالَةِ أَيْضًا مَا هُوَ مَذْكُورٌ فِي ٱلْفِقْرَتَيْنِ ٱلتَّاسِعَةِ وَٱلْعَاشِرَةِ .‏