Permanent endowments are typically restricted for use for a specific purpose. The vast majority of the time, that purpose is academic and scholarly pursuits, not athletics. Only a small percentage of ku's permanent endowment is for athletics, and they can access a small percentage of those funds every year based on investment returns on the holdings. Beyond that, they could borrow money from the foundation on a note.
ku like K-State appears to place specific capital giving in temporarily restricted accounts with the Foundation, for example right now or very recently K-State athletics had millions of $ in temporarily restricted or unrestricted accounts with the Foundation, but those aren't counted towards the permanent endowment.
A school could have a bazzillion gazzillion dollar endowment and unless the people who made those gifts wanted the proceeds of the investment return, or a % thereof to be used for athletics, it doesn't make a damn bit of difference for the athletic program. I guess athletics could get a bigger loan.