I'm glad Flex is coming back. I looked at "as needed" and didn't (insofar as I could see) allow me to select days to not water. And the "specific days" mode seemed to want to water every selected day.
My goal, as a user, is to tell the Rachio about my yard, what days I don't want it to water, and then walk away to enjoy my increasingly beautiful and water efficient yard. It can worry about soil moisture, next rain, weather, days it can't water and come up with the optimum watering schedule. I just want a nice yard I don't have to obsess over.