Joseph – it’s not the same at all. From what I’ve heard, there are heteirim to stop having kids at a certain point or to take breaks.
It’s certainly not the same level of chiyuv. You aren’t supposed to give mussar to people who won’t listen to you unless it’s something that’s an outright issur in the Torah. I don’t think this falls in that category.
In any case, if they just get married late, they for sure aren’t being “over” on anything.