"Clean before checkout" is not taken into account by the dev Jenkins jobs

Even with the "Clean before checkout" Additional Behavior, both jobs don't seem to actually clean the workspace:
https://qa.nuxeo.org/jenkins/job/Private/job/Mobile/job/nuxeo-mobile-master-android
https://qa.nuxeo.org/jenkins/job/Private/job/Mobile/job/nuxeo-mobile-master-ios/

As we can see in the logs, npm install doesn't do anything thus the old node_modules folder is kept:

15:22:58 + npm install
15:23:10 + npm run build-android

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This only happens on Multibranch Pipeline jobs.
Now using the workaround for https://issues.jenkins-ci.org/browse/JENKINS-37658 described here: https://support.cloudbees.com/hc/en-us/articles/226122247-How-to-Customize-Checkout-for-Pipeline-Multibranch

-                    checkout scm
+                    checkout([$class: 'GitSCM',
+                        branches: [[name: env.BRANCH_NAME]],
+                        extensions: [[$class: 'CleanBeforeCheckout']],
+                        userRemoteConfigs: [[url: 'git@github.com:nuxeo/nuxeo-mobile.git']]
+                    ])