I looked at the files, and the bug seems pretty obvious to me, I made a mod to fix it.
https://steamcommunity.com/sharedfiles/filedetails/?id=1624765234
If you have a save from before you fully ascended your species to Synth, please install and test this mod. Should be fully save game compatible. Let me know if it works and if it has any problems.
I dont usually play robots/synths, so I dont have any good save game candidates of my own. I did some basic console testing, I still prefer playtesting before im fully confident in a fix.
To clarify, normally the special project for Synthetic Evolution is supposed to force-change some of your Policies before it takes those options away. The vanilla files do that with your robots allows/disallowed policy, but it forgets to do that for your AI rights policy. This mod just adds the correct policy change before allowing everything else to operate as normal, so it should be very lightweight and not change the vanilla experience at all, except for fixing the problem, obviously.
Has anyone actually bug-reported this?