This is interesting and nothing I was aware of before. I will need to check into this.
In the past I deleted scheduled workouts (for example I deleted a swim when I did a run on one day) which might have taken differences of the daily and predicted weekly TSS. However, I noticed that by deleting the planned workouts it was not possible to determine at the end of the week if I was able to reach my weekly time goals for each discipline. Hence I started keeping both the planned as well as the performed workout. This would explain why the predicted TSS now is much higher than the daily TSS. Does this make sense?