In "Pipeline Syntax" page for "ws" step it says:

if you need to enforce that behavior, you can either fail (error) when pwd indicates that you got a different directory, or you may enforce serial execution of this part of the build by some other means such as stage name: '…', concurrency: 1.

..., whereas in "stage" step it says:

An older, deprecated mode of this step did not take a block argument, and accepted a concurrency parameter.