BUtterfield 8 is a 1960 drama film directed by Daniel Mann, starring Elizabeth Taylor and Laurence Harvey. Taylor won her first Academy Award for her performance in a leading role. The film was based on a 1935 novel written by John O'Hara in the wake of the success of his critically acclaimed "Appointment in Samarra".
Elizabeth Taylor was the leading role in the film, supported by Laurence Harvey.
The context only says that Elizabeth Taylor was the leading role, it doesn't specify whether Luarence Harvey was a supporting role. The system might have tripped on what "supported" meant in the statement.