The timeout step does not use the defined grace period. Which is 5s in testing and 60s in production. Instead it reuses the timeout which results enormous waiting times if the job is unkillable.

This example takes 20 minutes to complete instead of 11 minutes (10 minute timeout + 1 minute grace period):

timeout(time: 10, unit: 'MINUTES') {

    unkillable()

}