Can not pass variable as argument to a classmethod after colon from Url="/Example/:Variable"

When requesting /MDX2JSON/PivotVariables/Patients?Namespace Patients shoud be passed to a method but its not. When argument passed directly into the method it works.

<Route Url="/PivotVariables/:Cube" Method="GET" Call="WritePivotVariablesForCube"/>

Has something changed in IRIS and this syntax is deprecated, or is there a bug and the colon is ignored? What could it be?

This question is continuation from https://community.intersystems.com/node/534811