@Matt-HuserI'm no longer working in that project and as far as I know my colleagues put it on ice and are working on other aspects of that project until the customer decides if we should look for an alternative (a custom development, I guess) or wait for a future upgrade that eventually could improve this functionality and would justify an Enterprise upgrade to get the improved Arcade functions and rule functionality.
To name a few, we had issues with complex rules that worked in file gdb but not in an Enterprise GDB. Arcade lacks basic functions making some simple processing (like clipping intersecting features or making external requests) really difficult or impossible to script. Users wanted to use their own rules or disable GDB rules they didn't need for a particular task, but we didn't find an easy (or any) way to reach their needs. If you want to get new Arcade functions you have to upgrade Enterprise with all its implications (not something you want to be doing often).
I'm not saying attribute rules do not work at all but I think they are not suitable for this particular project we were working on.