Great suggestion, I have the same issue. Items that are Done but have a date in the future, still show in the google calendar as To be done. This is confusing.
My suggestion for a new automation would be:
When status X change to X, clear column X from this item.
This would be applicable to the Date and People column as wel. Also see When Status changes to DONE, Remove "Assignee" from People and Unassign when issue is set to done