Ecommerce Categories - Item placement

Gathering opinions on the placement of products in a category structure for Ecommerce, and the effect (if any) on SEO.

In some ecommerce packages your item can only be placed within a single category, in others you may place it in multiple categories on your site. And in some situations, your items will show in all parent categories when being placed in the child category.

Considering that each category page from parent to child - is optimized to the fullest extend (being all titles, meta tags, unique category description and content, etc...) like so -

Home->Widgets -> Round Widgets ->Blue Widgets
Home->Widgets -> Round Widgets ->Green Widgets
Home->Widgets -> Round Widgets ->Yellow Widgets

Would there be potential SEO impact (positive or negative) in showing the product items throughout the category path, rather than just at the last category?

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Thanks