Hi Kyle,
Concurrencies and route dominance is one of the remaining ArcMap equivalency items that still haven't been brought into ArcGIS Pro. Along with complex shapes, cover behavior, and external system integration, we'll be bringing it into Pro in the next few releases. The concurrencies REST endpoint is available with services published through either ArcMap or Pro that have the linear referencing capability enabled.
Nathan
Esri Roads and Highways team
