If you make changes to the Similarity Report filters for a specific submission and the similarity score updates, the updated score will not be transmitted to Canvas SpeedGrader.
This is expected behavior as we do not currently have the ability to pass updated similarity scores to Canvas SpeedGrader as a direct result of changes made to the report filters.
SpeedGrader will continue to display the original generated score that was produced based on the settings applied to the assignment. Any filters that are necessary for Turnitin assignments should be set during assignment creation before students start to submit. This will ensure that the similarity scores generated based on the filters that have been set for the assignment are the same scores that are passed to SpeedGrader.