Like Reha posted - why do we remember extreme cases? Are most practicing/religious Muslim men like the one u’ve described pak2015? It’s the same thing… either it’s ex prossies or Virgin marys. Normal people are not like that.. in an extreme case YES it would be imperative upon on the person to disclose certain things.
The majority of God-fearing men and women commit a major sin (since we are talking abt pre-marital relations) and repent… they don’t repeat it. For the sin they did commit.. must they tell their spouse? Unless it directly affects ur future (STD, child etc) I don’t think so. If ur pursuing a rishta u will see from behavior patterns what that person is like.. if u see an immoral woman, u will know. One sin does not make a person immoral and their confession does nothing but be a cause for embarrassment for that person.