Redirect link indexed as Page by GG : Good or Bad?

Dear SEO friends, I recently came across a website and was surprised to see the vast number of pages it had when I used the Google search command: site:www

However, as I clicked on some of the pages presented by Google, I was redirected to another site - specifically, when I clicked on a page with the URL MAINSITE.com/productXYZ, I ended up on a page with the URL SELLER.com/productXYZ. This redirection occurred for different sellers.

Upon further investigation, I discovered that the MAINSITE (which is an affiliate website) got indexed as page the sponsored redirection products of many of its affiliation programs. However, it doesn't appear in the search engine results pages (SERPs) because there is no real page. ( is like the website got 100 real page and 900 others redirection)

Finally my question this is useful for SEO? : Yes : Like got more indexed page? and maybe rank on it... No : The Sponsored redirect link should be in nofollow and no Indexed because it is the same title, meta description...

Thank you for your insights in advance!