The plugin option of "Prevent multiple jobs with identical parameters from running concurrently" is NOT preventing a second build from running, despite it sharing a parameter value with the already running first build.
It says in JENKINS-37809 the issue was fixed in v2.2, however I've tried with all versions starting from v2.2 all the way to v2.6, and all failed. 

Anyone aware of this and can suggest a solution or workaround?