InitializeSteppingVerbose in Single-threaded mode not working

Geant4 Version: v10.6.3 & v11.2.1
Operating System: Ubuntu 22.04.1
Compiler/Version: g++ 11.4.0
CMake Version: 3.22.1

I am trying to use a custom SteppingVerbose class, but it seems that only the default SteppingVerbose class is being used.
I introduce my verbose class via the G4UserActionIntitialisation class by using the InitializeSteppingVerbose() function, but it seems that this function is never called.
Could it be because I am running my programme in single-threaded mode?
When I check the source code, the InitialiseSteppingVerbose() function is only called by two RunManagers, but both are only used in multithreaded mode.
If my guess is correct, how can I introduce a custom SteppingVerbose function in single-threaded mode?
Thank you for any help.