After more testing, here is a better way to describe the issue of this bug.
The cache is being fully purged. So the issue is not really cache purging. The issue is that immediately following the cache purge during an extension being enabled or disabled, the newly generated cache files for specifically the acp_overall_header/footer.html files do not contain the newly enabled extension (or they still contain the just disabled extension).
So the issue is the ACP overall_header/footer are not being updated properly to reflect the enabled/disabled state of an extension during the enable/disable processes.
This is fatal for extensions that want to add any template events to the header or footer of the ACP.
But this goes for all extensions. Disable any extension, no matter what it does. You will see that there are stale references to it in the ACP overall_header/footer in the form of
I guess you could say its the ACP overall_header/footer template events that are not aware of the correct state of an extension after enabling/disabling.