The latest version (0.8) of the workspace cleanup plugin seems to cause Jenkins to think a job is complete before it actually finishes all post build steps. Going back to version 0.7 doesn't show this problem.

Example: See attached BuildSteps.png
'Results' is a job that blocks when upstream jobs are running. Jobs A, B, C, and D trigger the downstream job 'Results' and pass their current build parameters (which are all the same) using the Parameterized Trigger plugin (v2.14).
In the scenario where only one upstream job is still running (say all jobs completed except 'D'), the 'Results' job is blocked (waiting for job 'D'). This is correct.
However, once job 'D' got to the workspace cleanup post build step in its job configuration, the downstream job 'Results' would get triggered as if all upstream jobs were completed. This is a problem.
Then when job 'D' actually finishes cleaning up the workspace, another build of job 'Results' is triggered.