Any endowment argument is moot. First of all, it’s not like universities release significant amounts of their endowment for use each year. They might just use the minimum percentage required to maintain their status as a nonprofit organization for tax exemption. Endowments are complex and most of it is restricted, meaning that universities can’t choose what they’re going to use it for and when. For example, a business school graduate of Stanford may donate $100 million, but request that the fund should only be used to hire new faculty for the business school in the next decade.
In other words the endowment size isn’t even a good measure of the amount of resources that a school directly allocates for their current undergraduate and graduate schools. A school like Harvard, which has many graduate schools that offer almost zero financial aid, is going to have a larger revenue from tuition, than say Princeton. Even if they don’t release as much from their endowment, Harvard could spend more just by the revenue it gets from graduate school tuition.
If someone wants to go through the arduous (and ridiculous) task of looking at not only a school’s endowment release, but also its revenue from tuition, allocations of endowment money (what types of restrictions are placed for what amount), and detailed expenses, to truly asses the resources for each division in a given school, you can go ahead. But until then, don’t use endowment as an argument.