I think JOIN will only suggest one workout each day. So if you complete a workout and see that you have more time today you will have to pick the extra workout yourself.
Join will adjust the workout suggestions as soon as you complete a workout or adjust the availability.
JOIN is workout philosophy is very different from Xert. It prioritizes longer workouts and many rest days. Also, the threshold or VO2 max workouts will typically have easy zone 2 before and after the hard work to reach the time demand/constraint.