Here's my take: this is not an Apex dry dock issue but simply a dock availability issue in Southampton. The communication from Celebrity states that "These sailings must unfortunately be redeployed to accommodate an earlier dry dock schedule. Due to this change in dock availability, we must cancel bookings and reaccommodate guests to alternate sailings."
the Celebrity email also states that current passengers can rebook on the listed options including the November 9, Lisbon transatlantic before June 13, Celebrity will most likely start new reservations for the November 9, 2024 cruise after the June 13 deadline.
We were booked on the November 3 cruise and transferred our reservation yesterday to the November 9 sailing from Lisbon.