Email from Gabe Montero stated that:

1) "given" - we did not update our docs to explain that on upgrade we DO NOT remove imagestreamtags that existed in older releases, but are removed in the current release, to ease admins moving any deployments using the now removed imagestreamtags to newer ones.  Hence, the onus is on the admin to ultimately remove these older imagestreamtags.
 
So docs need to be updated.  The docs team is still in flight tring to finalize all the additions we've come up with for dealing with disconnected installs.  So we'll need to work with them to find out when they might have cycles for this next round of doc improvements.  Presumably a docs BZ from the customer case could be generated to track.