Why does the system sometimes set inaccurate data to the exact value?

Even though it is always said that Can Do does not change data on its own.

Can Do only corrects values when the truth requires it. Sounds a bit strange, but it is actually quite simple:

• If the start of an element is imprecise, the user does not know exactly when the element starts. However, if the status is changed from "in planning" to, say, "in progress", then the item has actually started and this can be known. Therefore, the start date is set to an exact date.
• The duration and work can also be imprecise. However, when the package is completed, it is effectively finished and the actual work and duration are known (and therefore recorded by the system).