My clock tells me at 9:30 pm to take an hour-long walk to close my rings.
I never, and I will never go for a walk (leave an hour long walk) at 9:30 am at night.
However, I have done HIIT workouts and yoga at 9:30 am at night. It seems like a simple solution for Apple to just check to see what workouts I've ever done around this time of day and make a calculation based on one of these workouts. If it tells me to do an hour's walk, it will never happen. If it tells me to do a 20-minute HIIT, well, I can only do that.