No matter the value passed in to a periodic trigger, it results in a period of 1 minute. (also noted in JENKINS-54877)

I suspect the hard-coded cron spec here is the culprit: https://github.com/jenkinsci/job-dsl-plugin/blob/45052e1545c4c30496cfdda1943a1d7eac998ccc/job-dsl-core/src/main/groovy/javaposse/jobdsl/dsl/helpers/triggers/MultibranchWorkflowTriggerContext.groovy#L20

Note that the trigger class itself actually does some comparison of the values to generate a roughly right cron spec: https://github.com/jenkinsci/cloudbees-folder-plugin/blob/master/src/main/java/com/cloudbees/hudson/plugins/folder/computed/PeriodicFolderTrigger.java