Why is the binding of Yitzhak the focus of the narrative more so than the attempted offering itself by Avraham?
'ה never told אברהם to slaughter his son. Rather he was commanded to prepare his son ("bring him up") to be an offering i.e. bind him (see Rashi's comment on Bereishis 22:2). Therefore it follows to refer to the event as "the binding of יצחק" because that was the actual test, to go up and bind him. Nothing more.