If you do that you must also provide an abstract class with default noop operations that filter implementations would extend. Otherwise you are back with backward compatibility problems.

KeyValueFilter was introduced in 7.0, or other backward compatibility problem you have in mind?

I believe Emmanuel is referring to if we added additional operations
to the filter, but I am not sure what other operations we would want
to add to it.  If anything we would probably make a different type of
filter specific to its use case.