How is this different from running flows in the builder directly?
The builder creates and edits individual flows. The management surface governs the collection of flows: ownership, review cadence, dependency map, health score, usage reports, retirement. A team with five flows can get by with just the builder. A team with 40-plus flows needs the management surface or the library drifts into unreadable sprawl. Both surfaces are included on every paid tier; teams opt in to management when the volume justifies it. The transition is nothing more than adding owner tags and review cadences to flows that already exist.