The MSC API is a fundamental part of the HA Singleton feature, so even though we'd rather not have people coding to the MSC API in general, we can't make it private. So no point deprecating it.

Part of the goal of deprecating was also to emphasize that the MSC 1 API may go away. But 1) that 'emphasis' was in the module.xml file, which likely isn't read by users and 2) IDEs and javac already warn about the MSC 1 API being deprecated and 3) it is unlikely WildFly will eliminate all of its own use of MSC 1 API any time soon.