Julia,
I managed to re-install a GP 2018RTM version (build 18.00.0400) and tested the requisition WF.. it does behave as expected when logged into GP with the correct domain user.. when I was logged in with my usual domain account in Windows, it would show the requisition list, but the counter would be 0.
Bellow screenshots shows the difference..
This GP session was started under the MR2012 service account (sorry I don't have that many domain users in my TEST system)
I believe that Microsoft likely changed some of the behavior of the Workflow engine between 2018 RTM and GP 18.2 / 18.3 or 18.4.
This is likely to work "by design" and Microsoft might done some enhancements to it. Please check which Windows Domain user you're logged in before starting GP, or try start GP under a different domain account.