I got a listening transcript (that has been cropped for the sake of simplicity) as follows
The context is about people who got (and still) married rather than people who will marry or people got divorced.
As far as I know, 結婚する is a punctual verb (瞬間動詞) so got (and still) married must be translated as 結婚している.
As you can see from the above screenshot, the book author seems to be inconsistent (and probably wrong) as 「結婚する人] means people who will marry and 「結婚した人」means people who finished their marriage (literally it means the people got divorced).
Am I wrong in this reasoning?