Any change in default behavior should be intentional and explicit; returning false is neither explicit or inform intention of change in behavior.

Take JQuery for instance. On the on(‘click”,…) event if a developer wish to prevent propagation he would need to attach a preventDefault on the event which indicates both intention of stopping the event and it is as explicit as it can be.

Dont know what framework it is but that seems as a poor decision that will give future issues with backwards compatibility.