The whole point of the break is to give Oda a rest. Releasing chapters now would mean that oda would just immediately come back to work and behind schedule.
I know, that's why I said that maybe they didn't tell us about the surgery in real time, but rather waited 2-3 chapters to release his message.
If Oda knows he goes into surgery when 2-3 chapters are ready on his part, and will release while he's healing, I think he'd be more relaxed and will only go back to work when he is truly recovered.
I mean, suppose he did the surgery when 1083 was out and 1086 was ready for editing, he could have 3-4 weeks of recovering from the surgery without having the fans worry about anything, while after the announcement was published he can take the coming weeks to start working on a new chapter without haste. If I was his editor, that's what I would recommend him.