Event: get by ID does not return the ID of a custom contact reference field

Having an event, with a custom field, which is a contact reference, I would expect to get back the civicrm ID of the contact, if I use the action 'Event: Get By ID'. Looking at the code of AbstractGetSingleAction, from which GetEvent derives, this seems to be taken care of by the function normalizeCustomValues.

However, if I set up a simple Formprocessor, which takes an event id and show me the results of GetEvent, I find that the contact name is returned instead of the id.

I am not sure, which part of normalizeCustomValues does not work. If anyone has an idea, I would be happy to provide a merge request myself.

I tested this on CiviCRM 5.58.1 and ActionProvider 1.121