Different url for simple products from a configurable product
I'm developing a new csv file to import products on Magento 2 as I did in the past for Magento 1. I exported some examples to understand how to build my new csv file and realized that now Magento 2 creates unique names and urls for simple products associated to a configurable product. For example, a shoe with size attribute generates urls like:
Configurable url: nice-shoe
Simple size 41: nice-shoe-41
Simple size 42: nice-shoe-42
I checked if these unique url work but I got a 404 error. Only configurable url work.
So, my question is to know why Magento is doing this and if I should create these unique url for each simple product to avoid problems.