In my parcel fabric design I have created additional feature classes that I want a field type to be "GUID" for a specific field (such as "created by record") and use these fields in my editing process. The fields function as all other fields do except when I go to use the "Set Default Attribute Tool". Unfortunately, the Set Default Attribute Tool appears to not allow this. Is there some reason why? The tools works as expected for all other field types. When using the "Assign Default to Field" interactively the field with a type of GUID does not appear (see below) and when I try to run the tool as a python script it errors. out. The work around I am using is to set the field type to be a Textfield but that is kind of annoying and its just not right.
This is not related to parcel fabrics and perhaps you would get the right people to respond to it if it were to be posted under the ArcGIS Pro \ Geodatabase community.
In any case. @Colin_Zwicker suggests that you can create an Attribute Rule that calculates a default GUID on feature creation.