When running a multibranch pipeline job with a repository that commits a series of random messages with no changes in the files of the commits, the changes report shows only the commits that change file contents. Commits that do not change file contents are not displayed as changes by the git plugin though they are reported as changes by scm.

Refer to the JENKINS-66885 multibranch pipeline job in my jenkins-bugs repository for the experiments that were used to check this behavior.

Changes report non-empty commits

Changes report in the UI of the multibranch job looks like this when commits are not empty:

Changes report empty commits

Changes report in the UI of the multibranch job looks like this when commits are empty:

Individual job page with empty commits

When the changes are not reported, still the "SCM" section shows that there were changes.

The summary page for the individual build shows the inconsistency very clearly. It reports one change yet in the "SCM" section