As a result of a recent premium support call, ESRI has logged...
ENH-000184434
Allow multiple layers that reference the same Utility Network Dataset or feature class in a web map.
Description of Enhancement
In Experience Builder and Field Maps, Utility Network traces should return/select features from all UN layers in the web, regardless of whether there are multiple instances of the same feature class present (typically separated out by filters or definition expressions, for example). Currently, the applications only display records from the first layer of a feature class the web map encounters. The same trace configuration using the same map and same trace flags behaves as expected in ArcGIS Pro.
Basically, this is referring to the inability of Experience Builder or Field Maps to return/select all features of a utility network named trace IF there are multiple layers referencing the same feature class (feature service endpoint). For example, if a map has a layer for Distribution Lines and one for Service lines (both in the ElectricLine feature class) - separated out by web map filtering or published definition expressions - the trace widget or Field Maps trace process will ONLY show the selection of the first layer the tool encounters in the web map JSON, essentially.
This is highly restrictive in web map authoring in order to return accurate trace results if UN feature classes cannot be separated out with multiple layers of the same data source. Either we won’t be able to utilize UN tracing in web applications or Field Maps, or the UI/UX will suffer.
