Condition when BCNF and 3NF are equivalent

Statement - "If a table contains only one candidate key, the 3NF and the BCNF are equivalent."
In the below image, relation is 3nf but not bcnf. But it has only one candidate key ie AB, so according to above statement it should be either both (3nf, bcnf) or nothing. Can somebody explain what i am missing here ?