I'm running into a problem like this. I'm currently using pytest to run test cases, and reducing execution time using xdist to run tests in parallel and publishing tests results to TestRail. The issue is when using xdist, pytest-testrail plugin creates Test-Run for each xdist workers and then publishes test cases like Untested.
I tried this hook pytest_terminal_summary to prevent pytest_sessionfinish plugin hook from being call multiple times.
I expect only one test run is created, but still multiple test runs are created.