Smart cycle and manual cycle soak are selectable for drip irrigation but they do not work. It’s been recognized as a defect in the programming, but they are working to fix it at some point in the future (hopefully).
Most people assume drip irrigation is low water output and that’s generally true for most home/consumer use. However there are a variety of drip irrigation output types and some of them are high water output types too, especially in the commercial agricultural business. The advantage is preventing wasteful evaporation on the foliage or humid environments for fungal growth. In this instance, soak cycles would be useful and even more so if you’re irrigating on a slope.
Like the helpful advice above, you can switch the nozzle type to something other than drip so that the soak cycles work.
I’ll warn you that in general, Rachio’s handling of drip irrigation with daily flex is a bit of an unpredictable mystery to me. I’ve had good success using my drip irrigation with monthly flex so far this growing season (I’ve already harvested my early season fruits). The daily flex in general requires accurate input in the advance zone settings, with the problem with translating drip irrigation water output into nozzle inches per hour.
The daily flex has been great with my non-drip (turf) irrigation.