Sencha Charts - Axis questions

I'm trying to learn the new Sencha Charts and I have two code questions about the nightly build, see below,

Code:

Ext.define('Ext.chart.axis.Axis', {
    xtype: 'axis',


    mixins: {
        observable: 'Ext.mixin.Observable'
    },
    ...
    constructor: function (config) {
        ....
        me.mixins.observable.constructor.apply(me, arguments);
        Ext.ComponentManager.register(me);  // <-- Why this call?  Axis is not a component.
        this.initConfig(config); // <-- Is this call needed?  initConfig is also called by the Observable mixin.
    },
    ....

Sencha Charts - Axis questions