The rain sensor acts like an on/off switch. When it’s activated, your system won’t water. Once it’s deactivated, the system can water again. So having the sensor activate and deactivate in the middle of your 3 days will not change the pattern.
I use Flex daily, so I’m not familiar with how the interval watering handles the rain. On Flex daily it will take into account how much rain you got and not water again until you need the water, but it will not be a predictable schedule like your every 3 days.