It is my understanding. The PTAB can and will do what they deem necessary according to the law. If they find the patent to be unpatentable... they will continue the IPR. No matter what the parties agree too.
https://www.law.cornell.edu/cfr/text/37/42.74
§ 42.74 Settlement.
(a) Board role. The parties may agree to settle any issue in a proceeding, but the Board is not a party to the settlement and may independently determine any question of jurisdiction, patentability, or Office practice.
(b) Agreements in writing. Any agreement or understanding between the parties made in connection with, or in contemplation of, the termination of a proceeding shall be in writing and a true copy shall be filed with the Board before the termination of the trial.
(c) Request to keep separate. A party to a settlement may request that the settlement be treated as business confidential information and be kept separate from the files of an involved patent or application. The request must be filed with the settlement. If a timely request is filed, the settlement shall only be available:
(1) To a Government agency on written request to the Board; or
(2) To any other person upon written request to the Board to make the settlement agreement available, along with the fee specified in § 42.15(d) and on a showing of good cause.
