The goal of using ActionScript for Ext JS was to control the comprehensive framework with static typing.

So we really didn't like magically appearing methods, and we also didn't want the developer having to declare five members for one config (the config property itself and its get-, set-, update- and apply-method). Thus, for ActionScript, we "faked" Ext being more modern than it was (and is) and pretended that you could use "real" accessors to access a Config's get- and set-method, and to overwrite these methods.