With respect, to the question/issues reported, this is actually intended behavior to support a temporary data/core layer during the execution of scripts of the CORE message port. Attributes/values can be changes within the scope of the loaded model (understood as a view(, used for further calculations and if you do not want to save, it would be discard when calling the CLOSE operation. An explicit SAVE_MODEL is needed to persist then in the DB. For the scenario you describe, the following construct would mark the model as modified:
1# Get the current modelid, if not yet defined
2CC "Modeling" GET_ACT_MODEL
3# Change an attribute value (of attribute "Object's name in this case) to a specific value
4CC "Core" SET_ATTR_VAL objid: (12609) attrname:"Object's name" val:"DEMO"
5# Explicitly mark the model as modifed
6CC "Modeling" SET_MODIFIED (modelid) modified: (1)