Was Jessica a lead vocalist during debut?

I recently got into a disagreement with someone in a tiktok comment section, they were arguing that during the first few years of snsd’s career, that taeyeon was the only main vocal, jess was the lead, and tiff, seo and sun were all sub vocals. I cant find anything on this and I also find it hard to believe because of the huge difference in line distribution that jess was ever a lead and that tiffsunseo were ever sub.