There's no law about modifying a fact table. If it's an accumulating snapshot that is tracking a process as it flows from one step to another, then the standard Kimball method is to update the record as it is modified.
If it's a transactional fact table where the measurements are taken all at the same time for one row, then updating is bad.
In your case, it makes a lot of sense to have an accumulating snapshot to measure this data, since it represents a "workflow", where there's an approval step before the entered results become the "truth".