Planning mode automatic fill the Timesheet

Good morning,
for many projects/activities we are using the "manual planning" functionality that allows a manager to allocate in advance the time of his resources.
What we realised is the following: if the allocation is still in the future, the Timesheet shows a small number of the left-top corner suggesting the number of hours indicated in the "manual planning"; if the allocation results in the past (as the time has passed), the Timesheet is automatically filled with the value assigned in the "manual planning".

Is this the expected behaviour? Is there a way to keep always the "manual planning" as a suggestion in the Timesheet and not as "done work"?

Thank you very much,
Silvia