I worked at McDonald’s a decade prior to that, and they were 10:1 then, too. I think it’s possible and maybe likely some other chains might have switched from being 8:1 to 10:1 since the market leaders already had that size. There are much better examples though than some isolated regional player’s beef patty sizes.

We used to buy half gallons and gallons of ice cream. Brands started selling 60 or 62 ounces instead of 64. Over the years, it’s gotten to where some brands sell 48 ounces - three pints - instead of 64.

Breakfast cereals have had similar shrinking sizes.