In all versions of our documentation (https://confluence.atlassian.com/bitbucketserver/data-pipeline-1064085003.html) for the Data Pipelines feature, it is unclear that the commits report includes only commits in the default branch.

In fact, when reading the documentation, there is this statement:
"The data pipeline performs a full export every time"

Suggesting to readers that there is no limitation.

Include a warning section at the top of the page with a clear statement that only commits in the default branch are included in the commits report

There is a feature request, https://jira.atlassian.com/browse/BSERV-19811, requesting that this feature be improved to allow for branch selection, but there has been no activity on that request for just under 19 months.