I visited just now. A milk bar is Australian/NZ lingo for a kiosk or very small convenience store where you can get drinks and snacks. In this case, the store has a sign that says "milk bar" but no non-generic `name`. I think that `amenity=cafe` with `name=Cronulla Station Milk Bar` would be best. Photo here:
https://cdn.discordapp.com/attachments/319388810385424384/1151995815871647764/IMG_20230915_073501.jpg