When a field has a domain assigned to it the field calculator allows an editor to calculate any value in the field and the geodatabase will accept the edit without validation. The geodatabase or the field calculator should be smarter and not allow users to circumvent the data design which is using domains for a reason.
If the geodatabase is going to require us to take regular tables and convert them to domains ridding the system of relational design. It should at least protect the data integrity it is trying to control.
This should also include the Calculate Field toolbox as it should have field value validations when dealing with a field that has a domain assigned.