Drupal Association members fund grants that make connections all over the world.
The documentation on post-load callbacks states that the callback is invoked with the argument being the libary, version and variant available.
This isn't the case. If you track the logic involved with the call to the post detect hook by the time the hook is invoked the variant and version context have both been lost.
The only way I've been able to get variant/version specific post-detect to work is to define the post-detect callback in the variant/version context and let the array_merge of variant/versions get the right post detect hook invoked.