The base offering is definitely not champagne but some sparkling, my partner would have tried the champagne at least but he went straight for the Heineken
And you are correct, not only the meals but also the bar has different offerings based on how you access the lounge and the staff will ask you to show boarding pass if you want anything beyond the standard range. Last August we had access through DragonPass so only had the base buffet food plus standard drinks, but according to my partner they did have a champagne in the fridge behind the bar as well, out of reach for him though lol. So who knows what is included with CI, will find out late May when I fly them from MEL.