I think it is also a little unrealistic for two kids in their early 20ies to sit and discuss how they see the rest of their lives and then expect them not to change this with a little experience. I'm not a fan of people telling anyone they'll change their minds on any specific issue, and of course people change throughout their whole lives. But early 20ies just usually lack so much experience and understanding of so many things that it's all theory and confusion.

Point being, probably best not to get married at this stage but if you do, no one can hold their partner hostage to things they thought they wanted or expect that just because they had a big talk it will mean something in the future