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.
( नीतिसूत्रे ३१: ११, ३०; १ पेत्र ३: ७) विवाहात आदराची भावना ही लग्न होऊन अनेक वर्षे लोटल्यानंतर येऊ नये.