Pipeline Job B was configured to trigger every time upstream Pipeline Job A completes successfully. After this configuration was removed, new successful runs of Pipeline Job A still triggered Pipeline Job B.

Initial Job B config.xml:

<org.jenkinsci.plugins.workflow.job.properties.PipelineTriggersJobProperty>
    <triggers>
        <jenkins.triggers.ReverseBuildTrigger>
            <spec/>
            <threshold>
                <color>BLUE</color>
                <completeBuild>true</completeBuild>
                <name>SUCCESS</name>
                <ordinal>0</ordinal>
            </threshold>
            <upstreamProjects>UpstreamPipelineJobA</upstreamProjects>
        </jenkins.triggers.ReverseBuildTrigger>
    </triggers>
</org.jenkinsci.plugins.workflow.job.properties.PipelineTriggersJobProperty> 

Making further updates to the configuration for Pipeline Job B still did stop the trigger from occurring. Using the groovy scripting console (<JENKINS_URL>/script) for both Job A and B, getting the WorkflowJob objects and checking getTriggers(), getTriggersJobProperty()?.getAllTriggerActions() and getTriggersJobProperty()?.getTriggers() returned empty lists as expected, suggesting the trigger behavior is cached or saved somewhere else when it should have been cleared when the configuration was removed.