My assumption : Lots of R1 Decisions have come out already - Stanford, Booth, Kellogg, Yale, Tepper, Goizueta, Darden, Ross etc. Fuqua’s decision date is 15th Dec. If a student has multiple admits from the above and has decided not to attend Duke over any of them - this helps free up a spot if they withdraw their app.
This has dual benefits - 1. The spot can be offered to another deserving candidate & 2. More importantly, improves Fuqua’s yield.