Exception on CA instantiation with Configurable._useGlobalInstances=True
CA Configurable deduplication doesn't work if the CA is not created with Configurable._useGlobalInstances=True. Conversely, generating CAs in this state can lead to errors of various types, including generating the wrong Sequencer types. So it would be far less error prone if the creation of a CA fails directly when invoked in a legacy job outside of the ConfigurableCABehavior scope.
Setting the full-unit-tests label in case there is any code that is (mis)using CAs in this context.