This is just a change to the way the fields are displayed. It is still possible to use a validated field to create a relationship to the validation object, by just using the field itself rather than the field_valid. For example, you can create a new relationship between Incident and Category, with Incident.Category on one side and Category.RecID on the other, and you will be able to push data between the objects without issue. In the list of relationships, the link field shows up as Category_valid, even though it is shown as Category if you click into it. You'll see the same behavior in the OOTB relationships IncidentAssociatesService and IncidentOwnerEmployee, for reference.