I've been around long enough to know mods would disable the achievements on me ;)
That explanation also wouldn't explain why all the other achievements remained completed, eg. the Agri science one in the photo which popped at the exact same time, as well as every other achievement that triggered in ...

I previously had this achievement from vanilla. After it's SA version was changed, I re-earned the achievement. It now seems to be tied to the save, if I load a save that hasn't earned it, it shows up in the in-game achievements list as not completed.

Me unlocking it in my first save
https://i ...