The documentation seems to clearly indicate that the User ID field defines the system user to run the program.
Does whatever you need require just the users permissions, or other environmental settings?
Maybe you need to also define a Profile is there are environmental variables that are needed.
https://docops.ca.com/ca-process-automation/4-3-1/en/reference/operators-reference/operator-overview/command-execution-operators/run-program-operator
Windows
The parameter defines the path to a batch (.bat) file in Windows that sets environment variables to run by the process.
The variable settings that the batch file that is specified here defines are additional to any variable settings that are defined for the user profile that runs the process. If no file is specified for this option, the operator uses the settings that are defined by the Shell profile parameter set for the Windows process service.
How are you verifying the user that is being used after the instance runs?