I don't recall them being stingy on the Champagne, but rather the crew not being proactive to offer refills. Often times you have to ask them to fill up your glass, as opposed to other airlines where a good crew will keep topping up your glass until you say stop. On intra-EU flights they don't give you the whole miniature bottle, despite asking for it

I flew SWISS Business Class GVA-ARN last week, fantastic crew who were more than happy to keep the glass full throughout the flight. I was the only one who had Champagne so they probably wanted me to finish the bottle rather than have it go to waste by pouring it away before landing. But then again the difference in crews between then and TK is night and day.