Unfortunately, I couldn't get it to work, no matter how I set up the timing. Seems like testing for languages known in a bootstrap is just too damn hard! I even found another thread from 5 years ago where someone was trying to do the exact same thing I'm trying to do (create custom Rings of Eloquence that automatically add languages without creating duplicates). I tried the exact things suggested there, and none of them worked.
https://forums.wolflair.com/showthread.php?t=60650