I had a real strange experience with surrenders in my game that I thought might be due to the new surrender mechanic. I do have surrenders on in this game.
In the same turn the Yor, Snathi and Terran Resistance surrendered to me. I then received messages that the Yor and Terran Resistance had been destroyed, but I didn't receive a message that the Santhi had been destroyed. Right after that the Xraki surrendered to me, and I received a message that they had been destroyed. This was in 3 or 4 turns starting on turn 75.
Later, I saw that the The Measured had been destroyed by the Snathi, who had surrendered to me earlier.
Even later, I saw that the Tywom had also been destroyed by Snathi.
The continuation of a race that had surrendered is not new because of this update. I have seen and reported it in earlier versions. It seems to be due the timing of the various threads that are being used by the game. In this case, the Snathi surrendered in one thread while some other race surrendered to them in another thread.
I felt it would be good to send in a save before this happened so it could be checked to see if things were working as expected when the mass surrender occurred. I loaded an autosave before it happened and resumed playing. I saved each turn to get one just before it happened to reduce the playing time needed by the Devs.
Only the Snathi surrendered to me.
Nothing else happened the way I just reported. Races are still surrendering to other races, but it seems like things are going the way they did in the past, with no mass surrendering to me or any other race. Races that surrendered are no longer in the game.
I decided to report it so that others will be aware that something like this could happen.