Mongo.logout() doesn't go through runCommand(), which is where the stepdown suites catch and retry on stepdown errors. The stepdown suites aren't meant to test auth, so tests that call logout on a mongo object should be blacklisted from them. One way to do this is to override Mongo.logout() to throw in these suites (like what's done here) and add the tag requires_non_retryable_commands to any tests that use that method.