Observed in https://ci.jenkins.io/job/Plugins/job/workflow-support-plugin/job/PR-30/5/flowGraphTable/ that of the four branches, the first three are displayed as

Branch: linux-8 - (1 ms in block)

whereas only the last shows a real time:

Branch: windows-8-2.32.2 - (17 min in block)

Unfortunately I do not know what plugin versions are being run here so it is possible this no longer reproduces with current code, but it should be easy enough to check: just run a build with parallel that will sleep for a while in each of several branches.