I've got a matrix job, that is triggered by the Gitlab plugin through webhooks.
Job configuration contains configured "Gitlab connection" in General settings and 3 postbuild actions: "Add note with build status on Gitlab Merge requests", "Add vote for build status for Gitlab Merge requests" and "Publish build status to Gitlab commit".
It also contains a secret token in the advanced settings for Build triggers, and this token is entered in the settings of the Gitlab project.
Configured build trigger is the only "Build when a change is pushed to GitLab. GitLab CI Service URL: "
Console output contains 4 messages "No GitLab connection configured", one after git checkout and before build start, and 3 more in the end of the log.
The respective merge request in Gitlab contains messages like
"Administrator @root commented about an hour ago
:white_check_mark: Jenkins Build SUCCESS
Results available at: Jenkins matrix_job #66 "
that suggests, that build statuses are actually reported