Not familiar with the implementation, so maybe this is incorrect, but does Wendy’s tell you when you’re paying more or less? If not, my primary issue would be transparency. I know to show up for happy hour or lunch and I know what the prices will be.
I don’t want to have to memorize the prices because they quietly bump up everything on the menu by $0.50 at peak meal times everyday for an hour and don’t indicate that anywhere.