I am going to explain why N count is unimportant when it comes to selecting a partner.

First of all, I do believe promiscuity in general might harm someone's chances of being a good partner and a higher N count might indeed mean lower chances to have successful relationships.

However, there's a problem. How can one know the truth about N count? It's close to impossible in many cases. Even back in the day when marrying virgins was the norm, some women still had hymenorrhaphy. In fact, my grandmother has told me stories of women she knew having hymenorrhaphy in secret in order to get married.

https://en.wikipedia.org/wiki/Hymenorrhaphy

This is a thing that happens even today.

To sum up, it's pretty much impossible to know for sure the N count of another person. How can you be sure they didn't lie or they didn't remember well? The more a high N count is taboo, the more likely women are to lie about N count. Therefore, N count is not an accurate method of calculating someone's value as a partner as it's impossible to know the truth.