Inside a FieldConfigurator defined on an associated CollectionField's entity, $entityDto->getInstance() returns NULL

CRUD of entity "A" includes a CollectionField of entities "B". I'm trying to define a FieldConfigurator on B's fields. When I modify an entity of type "A" which has some associated "B"s, the configurator is correctly called also on B's fields: inside the "supports" method $entityDto->getFqcn() == B::class returns true, and $field->getProperty() returns their names, but $entityDto->getInstance() always returns null.

If instead I define the configurator on A, $entityDto->getInstance() correctly returns the instance, but I don't know how to access B's Fields and EntityDtos from there, to configure them.

Start by tracing FieldConfigurator's supports method when it is invoked for fields inside a CollectionField, then inspect how EntityDto instances are populated for the associated B entity. Reproduce the A/B CRUD case described in the issue and determine the expected way to access B's instance or fields; done when the behavior or supported access path is covered by a regression test.