Element visible via a checkbox in JSXGraph: altering other parameters?

Assume you have the following elements added to your JSXGraph board:

var checkbox1 = board.create('checkbox', [1, 0.5, 'Click me']);
var p = board.create('point', [1, 0], {
        visible: function() {return checkbox1.Value();},
        label:{offset:[15,15]}
});

Why is it that the presence of the function inside visible alters the values given inside label? (By commenting the line visible..., you notice a difference.)