Hi Josh,
Not sure where you were searching...
Yes, there are some current limitations with Attribute Rules, like currently there are only calculation rules and constraint rules. This is explained here Attribute rules—Geodatabases | ArcGIS Desktop
That help also explains that
There is currently no cross-layer or cursor support for attribute rules. Attribute rules are only supported on the row (feature) being evaluated. Attribute rules are currently only supported on enterprise geodatabase datasets.
which is what you're looking for with the intersection type method from Attribute Assistant.
In the ArcGIS Pro Roadmap - September 2018 you can see that Attribute Rule enhancements are top of the list with this explanation,
- Attribute Rule Enhancements – Additional user experience for creating and modifying rules, existing rule validation, and support for querying additional layers as part of calculation or constraint-based rules.
As for why Arcade? Using Arcade expressions allow them to be understand (and thus executed) across the platform meaning that instead of having Attribute Assistant methods locked to your desktop, Attribute Rules maintain data integrity and speed up editing no matter where you're working with the data.
ArcGIS Arcade | ArcGIS for Developers
I hope this is helpful.