I hear this all the time, but I've actually never left a manager. I've liked all of my managers. It's usually either some external force like a compelling opportunity or something with the org that is beyond my manager's control.
That saying really isn’t true. I know plenty of people that liked their manager but still left companies. There are plenty of reasons people leave companies that have nothing to do with their manager.
i’d say it was at least half true —i’ve definitely left both companies and managers!