EP will link products only if you TELL it to do so...
How does it happen ?
The most common "error" is when you decide to change a category / sub-category that a product is in... so you make relevant changes in your spreadsheet to v_categories_name_1 and (possibly) v_categories_name_2, etc...
... and you then run the file through EP.
EP then sees that the v_products_model is already in an existing (and different ) category/sub-category so it says:
"OK... the product is already in catgegory ABC, but this current run of the spreadsheet says it must also go into category XYZ...
... and it dutifully LINKS the products for you!
How do you avoid this? well, there is only one way (if you use EP) and that is to move products to other categories MANUALLY through the admin console, then make a note of its new location so that future imports (via EP) will have the category tree correctly structured for that specific v_products_model.
Sadly, while EP remains the most efficient way to mass-upload product data, it has some drawbacks that are not easy to solve, and product moving procedures is one such drawback...