I agree with you that good planning makes it easier to keep assets separate, and I think Harvard is assuming that for second marriages, which might be recent, the parents have done that and that’s why Harvard instructs that the assets be listed separately if possible. However, it is not required to do things the easy way and many people insist on doing them the hard way!
I disagree that all earnings and assets in a marriage or that come into a marriage are joint. I think there are 9 community property states. In those, it is a little clearer how to deal with earned income, but assets include things other than earned income and even income can include payments from sources that were pre-marriage. In the other states, there can be a lot of different considerations including obligations of one spouse (debt, child support, IRS payments) that make the earnings not marital property from the get go. All kinds of different situations. One spouse might be getting funds from a family trust, they might file separate tax returns for medical expense reasons, they might live in different states and have different tax obligations, they might be getting child support payments that are deposited into a joint account but that are not marital property.
Harvard recognizes this and asked the family to separate if possible. If not, or the family doesn’t want to have the assets considered as separate, then they can just divide things in half. Harvard is giving the applicant the opportunity to show that the money all really belongs to a stepparent, or exactly where it came from. I don’t think they are going to question the division, and of course Harvard is free to just ignore the division. It is certainly within its province to just say ‘Nope, there is plenty of money among these 4 parents, so FA denied’ but why would they ask for assets to be separated if they are just going to lump it all together again? It appears that over the years H has learned that all is not even in a second marriage, that the stepparents are not always willing to fork over $60 grand a year for the child who has just joined his/her household last year.
If Harvard didn’t recognize the issue of stepparent money, it wouldn’t ask.