Hi,
This is quite confusing to me 
I tried several OpenMPI / MPICH / OpenPBS versions, and got the result:
MPI / OpenPBS / “Time Use” update?
OpenMPI 3.1.6 / 20.0 / OK
OpenMPI 4.1.2 / 20.0 / NO
OpenMPI 3.1.6 / 23.06 / OK
OpenMPI 4.1.2 / 23.06 / OK
MPICH 3.4.1 / 20.0 / NO
MPICH 4.1.2 / 20.0 / NO
MPICH 4.2.0 / 20.0 / NO
MPICH 3.4.1 / 23.06 / NO
MPICH 4.1.2 / 23.06 / NO
MPICH 4.2.0 / 23.06 / NO
All these tests uses the same job script to run HPL with GCC + OpenBLAS and the MPI of choice.
So… so far I can’t get MPICH time update work with OpenPBS.
It worked with Torque a long time ago though.
I’d love to know if anyone had similar problem and get it solved 
Mike