Share 5.2 is compatible with a 6.0 repository.
When starting the ACS Enterprise trial (https://github.com/Alfresco/alfresco-acs-trial ) and logging into Share the first time the following error is displayed:
You're using Share Services version 5.2.0. For Share to run correctly you need to user version 6.0.0.
1. The check should not be against the repository version 6.0.0, but should be between the Share version 5.2.f and the Share Services versions 5.2.f.
2. If the share services are incompatible with a given repository version the MMT tool should not install the AMP on the repository. Generally this is not the case moving forwards.
The same issue is seen in ACS community releases as they too are now 6.0._-ea.