I know it doesn't address your question, but the NW WorldClubs I stopped by had complimentary liquor drinks, though no bartender so similar to what you describe as the MLL. They also had some computer terminals and printers/copiers in the hub clubs. The only thing I could match it to was the Envoy club in PHL.

I'm not sure why NW and US would have such different club products, but I did find it interesting for my admittedly limited visits to airline club lounges.