Welcome to PBC. Here's how to use affiliate links for Idea Pins https://help.pinterest.com/en/business/article/tag-products-in-your-idea-pins
Please 'accept as solution' if this answers your question.
Some months ago, there were goals requesting you to tag products (even with affiliate links) so it used to work before.
This month, a client of mine submitted a pin with affiliate links without knowing this rule, and it got approved. I don't know if it's ok or if this one was an exception.
I think we should contact the Help Center and see what they say. Maybe someone has already contacted them? I'll do it today and update this post with the response I receive.