Personally I have found the exact opposite of your observation. The actual perk for non-haven guests, that need the assistance of a concierge, is provided by the General Managers (HD) secretary. Occasionally the HD will put you touch with the actual concierge and you will be treated the same as any Haven guest. Personally I have received much better service from the secretary than I have from most concierges
As for pre-cruise concierge access that is strictly for Haven guests.