I think that perfectly aligns with their take.
People in their 30s, married, tend to have more stable lives. They are in a position where they feel they are able to give that child a good life.
That actually makes sense. I think I broadly agree with this. Maybe we can do 100 different little things to help people feel like they are "set up".
Peak fertility though is early 20s. By the time people are in their 30s, having trouble getting pregnant is a more common problem.