Marketplace Management can recognize your variation relationships for an easier publishing process
Marketplace Management utilizes many sources to consolidate product-rich data and this can include a variation relationship between different items.
At this time, Marketplace Management will automatically import your variation relationships from Amazon and associate the items together. If your products do not exist on Amazon (and are imported from eBay or Shopify or another sales channel) then the variation relationship will not be established automatically for you.
There is a chance that the singular product you're selling on Amazon was created as part of a variation set. You might notice these Products within your Products Workspace under the Amazon ASIN number.
If you are selling the singular item and you do not want to sell the product as a variation set you can remove the variation association.
For instruction on how establish a variation set, please review this article
For instruction on how to de-link a variation set, please review this article.