A user should not be able to authorize an ArcGIS Pro Single Use license if it was installed with a per-user option. An attempt to do so returns a warning message:
"This functionality is not available without the ArcGIS Pro Licensing Service being installed. The service can be installed by running the license service installer located within the ArcGIS Pro installation folder."
As indicated by the message, the ArcGIS Pro licensing service must be installed to enable the Single Use authorization option for ArcGIS Pro.
There is another case, when installing Autodesk AutoCAD on the same machine as ArcGIS Pro, where ArcGIS Pro may act as though it is enabled to authorize Single Use licenses. In such cases, a user has access to authorize ArcGIS Pro using the Single Use authorization option. Doing so, however, results in an authorization failure.
The ArcGIS Pro licensing service, which is necessary to enable ArcGIS Pro to authorize Single Use licenses, is based on the FlexNet licensing service. Any application which installs the FlexNet licensing service, such as AutoCAD, triggers ArcGIS Pro to enable the Single Use licensing authorization option. However, doing so results with a failed license authorization. The Software Authorization Wizard for ArcGIS Pro uses a different version of the FlexNet Publishing toolkit. The copy of the FlexNet license service installed on the system must be the same or later version.