I’m not sure the PHP-Typography library – which is used in the Better Typography Grav plugin – deals with this case… But I kind of remember that the library can be extended with new locales and rules.
It would be ideal if the plugin would allow you to create a list of words that should not appear at the end of the line (in Polish these are some two or even three letter words).
I’m not using Grav for any project at this time so I don’t know if I could work on that ; but if you have any idea on how to implement this, feel free to write a PR