Git plugin 4.1.0 adds many GitSCM getters to the Pipeline approved list as part of JENKINS-42860 so that Pipeline users do not need to specifically approve a script that refers to GitSCM fields. It is confirmed to work when the references are directly inside the Jenkinsfile, as in the JENKINS-42860 automated check.

It fails to approve the reference to that field when it is accessed from a shared library method like GitUtils.my_utils

The failing reference looks something like this:

@Library(value='globalPipelineLibraryMarkEWaite', changelog=false) _

import com.markwaite.GitUtils

def branch='master'

node {
  stage('Checkout') {
    def my_utils = new com.markwaite.GitUtils()
    dir(branch) {
      checkout([$class: 'GitSCM',
                branches: [[name: branch]],
                userRemoteConfigs: my_utils.adjustRemoteConfig(scm.userRemoteConfigs[0], branch)
               ])
    }
}