Nitpicking.
According to the Settlement Agreement notice CAN be given sooner than June 1, 2026. The first requirement of a withdrawing school, as per the settlement agreement is:
"filing an official Notice of Withdrawal with each of the Members and the Commissioner ON OR BEFORE JUNE 1, for the withdrawal to be effective June 30 of the following year". So yes, a program could advise the ACC in the Spring, or at any time apparently, that they plan on withdrawing from the conference. Just has to be done NO LATER THAN June 1, to be effective the following year.