Behaviours don't preset or lock issue type field

import com.atlassian.jira.component.ComponentAccessor
import com.onresolve.jira.groovy.user.FieldBehaviours
import groovy.transform.BaseScript

import static com.atlassian.jira.issue.IssueFieldConstants.ISSUE_TYPE

@BaseScript FieldBehaviours fieldBehaviours

def constantsManager = ComponentAccessor.getConstantsManager()
def queryIssueType = constantsManager.getAllIssueTypeObjects().find { it.name == "Improvement" }
getFieldById(ISSUE_TYPE).with {
    setFormValue(queryIssueType.id)
    setReadOnly(true)
   setDescription("This is a description from a behaviour")
}