I've seen this happen sometime, but not always:
taavi@deploy1002 ~ $ scap backport 947361 947362 11:22:08 Checking whether changes are in a branch and version deployed to production... 11:22:08 Change '947361' validated for backport 11:22:08 Related change 947361 found for 947362 11:22:08 Change '947362' validated for backport The following changes are scheduled for backport: +--------+-----------------------------+--------+----------------------------------------+ | # | Project | Branch | Subject | +--------+-----------------------------+--------+----------------------------------------+ | 947361 | operations/mediawiki-config | master | throttle: remove expired rules | | 947362 | operations/mediawiki-config | master | throttle: add rules for Wikimania 2023 | +--------+-----------------------------+--------+----------------------------------------+ Backport the changes? (y/n): y 11:22:11 Voting on 2 change(s) 11:22:11 Change 947361 approved 11:22:11 Change 947362 approved 11:22:11 Waiting for changes to be merged. This may take some time if there are long running tests. 11:22:57 awaiting-backport-merges: 50% (ok: 1; fail: 0; left: 1) Gerrit could not merge the change '947362' as is and could require a rebase
Here 361 and 362 were stacked and merged within seconds of each other:
14:22:57 <+wikibugs> (Merged) jenkins-bot: throttle: remove expired rules [mediawiki-config] - https://gerrit.wikimedia.org/r/947361 (owner: Majavah) 14:22:59 <+wikibugs> (Merged) jenkins-bot: throttle: add rules for Wikimania 2023 [mediawiki-config] - https://gerrit.wikimedia.org/r/947362 (https://phabricator.wikimedia.org/T343595) (owner: Majavah)
Running scap backport after the merge completes normally, however.