In the e2e serial tests for the baremetal platform, the teardown cleans up any additional extraworker added by the current test and waits for its deletion. For some particular lengthy tests (such as "[sig-cluster-lifecycle][Feature:Machines][Serial] Managed cluster should grow and decrease when scaling different machineSets simultaneously [Suite:openshift/conformance/serial]"), this additional wait could occasionally exceeds the default test timeout (set to 15m).
Verified by e2e-metal-ipi-serial-* CI jobs
Closing based on comment #1.