A Shopify product with three sizes isn’t really one item in a spreadsheet - it’s three, each with its own price, SKU and stock status. The variant-rows format reflects that: every variant gets its own row, with the parent product’s details (title, vendor, type, tags, description) repeated on each one.
That gives you 26 columns per row, including option1/2/3 for things like size and color, price and compare_at_price, and both the variant’s own image and the full image list for the product. It’s the format this tool uses by default, and the one most spreadsheet and pricing work is built around.
Prefer one row per product instead? There isn’t a collapsed view today - variants are usually what you need the row-per-row detail for in the first place, like distinct prices or SKUs per option.
A t-shirt sold in three sizes and four colors, for instance, can have up to twelve variants - each one gets its own row here, with the shared product details repeated so the row still makes sense on its own when you sort or filter by size or price alone, without needing to look back at a separate product row for context.