In the SAFe work item hierarchy, Features are decomposed into what?

In the SAFe work item hierarchy, Features are indeed decomposed into Stories. This is supported by the information found in the SAFe Requirements Model, which outlines that a Feature is described by a phrase, benefit hypothesis, and acceptance criteria, while a Story is elaborated by a user-voice statement and acceptance criteria. These artifacts replace the traditional system and requirements specifications with new paradigms based on Lean-Agile development. Stories are the primary artifact used to define system behavior in Agile and are short, simple descriptions of functionality told from the user’s perspective and written in their language. Each implements a small, vertical slice of system behavior. The detailed implementation work is expressed through stories, which comprise the Team Backlog12.