E.g. see T223738#5209107.
Change 512231 had a related patch set uploaded (by EBernhardson; owner: DCausse):
While commit has:
Author David Causse
That is a cherry pick from master that has been done by Ebernerhardson, once why he is listed in the by part. One can see it as the performer. The patch author was DCausse and is thus listed as the owner.
The patch on master https://gerrit.wikimedia.org/r/#/c/mediawiki/extensions/CirrusSearch/+/511455/2 had an edit:
Change 511455 had a related patch set uploaded (by Jforrester; owner: DCausse)
Author: David Causse
In that case its correct.