Compilation error when accessing a protected super class field from a closure using owner, delegate or thisObject qualifier (different package)

new GroovyShell().with {
  evaluate '''
    package a
    
    abstract class Abstract {
        protected String protectedField = 'field'
    }
    assert true
    '''

  evaluate '''
    package b
    
    @groovy.transform.CompileStatic
    class Concrete extends a.Abstract {
        String doThing() {
            'something'.with {
                return owner.protectedField // `thisObject.protectedField`, `delegate.protectedField` fails too
            }
        }
    }
    assert true
    '''

  evaluate 'assert new b.Concrete().doThing() == "field"'