We chose a somewhat out-of-the-way name for this config (though it is in legue with "xtype" and "xclass") to not be confused with "override" in Ext.define. It is also something you probably don't need very often. The reason this is even present is that the underlying ability this config uses was needed by Ext.define/override to deal with singletons.
Also, the reason this is only applicable to components is that not all classes have the "config" concept as part of their design. Many classes do, but not all in the framework. And very likely not all classes in user applications.
The good news is that the functionality is now provided by Ext.override when the target of the override is an instance and not a class (which was previously an supported thing). The internal method Mitchell mentioned has been removed in favor of providing this functionality to any class or object via Ext.override.
Turkiyenin en sevilen filmlerinin yer aldigi xnxx internet sitemiz olan ve porn sex tarzi bir site olan mobil porno izle sitemiz gercekten dillere destan bir durumda herkesin sevdigi bir site olarak tarihe gececege benziyor. Sitenin en belirgin ozelliklerinden birisi de Turkiyede gercekten kaliteli ve muntazam, duzenli porno izle siteleri olmamasidir. Bu yuzden iste. Ayrica en net goruntu kalitesine sahip adresinde yayinlanmaktadir. Mesela diğer sitelerimizden bahsedecek olursak, en iyi hd porno video arşivine sahip bir siteyiz. "The Best anal porn videos and slut anus, big asses movies set..."