Simple Jenkins configuration, 1 master, no slaves. My project has 1 build trigger: "Build when a change is pushed to GitHub". I also have "Execute concurrent builds if necessary" enabled.

If a new trigger occurrs as a result from a push to GitHub, the concurrent workspace is not created. Jenkins waits until the current request is complete, then starts. If there were 2 queued up, it only executes the 'latest' one.

If I use a custom workspace, the concurrent builds DO work. Unfortunately, I cannot use this option as each of the workspaces need to be unique.