I am not sure if this is a bug or a design change, but it certainly seems like a major breaking change.
Traditionally Ext and Touch used to apply a Component's config to the Component itself, e.g.:
After instantization, both title and customKey fields were available on Panel directly.
title: 'My title',
Touch 2 Preview releases changed the config behavior where configuration is applied with an underscore which I understand is a private detail, and one should use getters/setters to access the config option.
But custom values were still applied to the component directly, so customKey was still available on Ext.Panel. This seems to have changed in Beta 1 and customKey is no longer applied to a component, its only available through initialConfig.
This potentially is a major breaking change that can a very large portion of codebase built on Touch (it has certainly done so for mine).