To help with this scenario (it is pretty specific):
You have a table that has columns that you do not know about when you create the dacpac, possibly you have a customer who modifies your schema after you deploy. If you deploy your dacpac those columns will be dropped which is bad and you don't want to completely ignore all changes to a table what do you do?
You can now use the new version of my deployment contributor with a filter like SqlPackageFilter=KeepTableColumns(Employees)