It appears that not all template files are being purged from the cache during the Enable and Disable processes of an extension. It appears the ACP template files do not get purged.

However they are all purged when choosing the Delete Data option during the Disable extension process.

As an example, I have an extension that adds an external JS file to the ACP's overall_header file via template event. Upon Enabling the extension, the cache must manually be purged in order to get the extension's JS feature in the ACP working.