That one would be tricky to implement without defaultSelectedLabelProperties. It's worth noting that defaultSelectedLabelProperties was intended for font styles, and not something like the visible property.
You could listen for Event.CHANGE and hide the label when isSelected is true. Perhaps by setting hasLabelTextRenderer to false.
Otherwise, you could use labelFactory to give the text renderer a name, and use getChildByName(). Then, you can set any property that you want on the text renderer.
button.labelFactory = function():ITextRenderer
var textRenderer:TextBlockTextRenderer = new TextBlockTextRenderer();
textRenderer.name = "button-label";
var textRenderer:TextBlockTextRenderer = button.getChildByName("button-label") as TextBlockTextRenderer;