git plugin do enforce all matrix axes do build the same revision, as identified by matrix head (see https://github.com/jenkinsci/git-plugin/blob/master/src/main/java/hudson/plugins/git/GitSCM.java#L845)

repo plugin must do the same. If jenkins instance don't have enough executors, some builds may actually run after first axes completed, and checkout more recent revisions, reporting wrong revisions in the matrix build status.