From the https://files.opcfoundation.org/schemas/RSL/1.0/Opc.Ua.RSL.NodeSet2.xml

<UAVariable NodeId="ns=1;i=6038" BrowseName="1:PositionFrame" ParentNodeId="ns=1;i=5006" AccessLevel="3">
<DisplayName>PositionFrame</DisplayName>
<References>
<Reference ReferenceType="HasModellingRule">i=78</Reference>
<Reference ReferenceType="HasTypeDefinition">ns=1;i=2003</Reference>
<Reference ReferenceType="HasComponent">ns=1;i=6039</Reference>
<Reference ReferenceType="HasComponent" IsForward="false">ns=1;i=5006</Reference>
</References>

PositionFrame does not have a DataType, but it has a TypeDefinition of NodeId="ns=1;i=2003" BrowseName="1:SpatialLocationType".
SpatialLocationType is abstract, because it is a "supertype" which should be subtyped for use and can not be implemented. The CartesianFrameAngleOrientationType is useable SubType described by this specfiication.

This construct was choosen to provide other groups the possibility to define their own SubTypes of SpatialLocationType with concrete definition of Postion and Orientation.

Sorry - I cannot understand this issue.
Is there an issue in implementing this nodeset?

The nodeset cannot be used as a base for an OPC UA server without modifications. Why would I need to edit the nodeset to make it work? You chose this construct to let other groups the possibility to define their own SubTypes, but in this way the HAVE TO make their own SubTypes otherwise the nodeset is not valid for a server.

The nodeset includes the CartesianFrameAngleOrientationType as useable SubType. If this kind of SpatialLocation-description fits to what has to be represented, then the nodeset can be used without "modifications"
@ma_robox: right?

The intention of the workgroup was not to define each kind of representable location (and orientation) information. Inside the specification are examples how to define own "not abstract" SubTypes of SpatialLocationType for use. (Annex E)

@ma_robox: What do you expect to be modified or the extended to the specification or nodeset?

No, the nodeset should work as is. I do have to edit the variable type to "select" a working SubType.

The NodeSet is correct and works as it. You are actually not allowed to change the standardized TypeDefinitions.
In OPC UA, it is allowed that an InstanceDeclaration is abstract (see https://reference.opcfoundation.org/v104/Core/docs/Part3/6.2.1/ ).
Only on the instance you have to use a concrete Type.

@ma_robox: can I close this issue with resolution "no change required"?

yes