You can certainly bind off each section, seam them and then pick up sts around the neck (72sts) and knit the neckband. You can either join all 4 sections, pick up sts and knit the neckband in the round or leave one seam open, pick up and knit the neckband and then close the 4th seam as the pattern instructs.
I think the pattern is just trying to save the extra step by keeping the final row of live sts in each section so that you don't have to pick up sts.
I like working into yarn overs and they certainly are a big part of the look of this poncho. Enjoy finishing the remaining sections!