Hmmm this sounds like it might be due to a partially failed update or an issue with the opcode cache on your site. Can you try forcing an update of the plugin (or deleting it and reinstalling it)?
This was already a fresh install from the repo, but I deleted and reinstalled it. Still doesn’t work. It’s weird; this worked well before. The function also clearly isn’t final.
As far as I can tell, there should be no opcode caching on the site. The only plugins I have active are ACF, Relevanssi stuff and Query Monitor.
I deleted the symlink, and that made the fatal error to pop up on every page load, not only on the plugin activation… but yeah, it points to the correct location.
I shut down the site in Local and restarted it. That did it. Sorry to waste your time without trying to turn it off and on again; I did try switching the PHP versions so I would’ve thought that would do it, but apparently not =D