The rumor is that Olympus was invited to join the L-alliance in January, but they decided to stay out:
https://photorumors.com/2018/09/28/...r-olympus-was-invited-to-join-the-l-alliance/
https://photorumors.com/2018/09/28/...r-olympus-was-invited-to-join-the-l-alliance/