Is the “Immediate” timing of an Input constraint implemented yet? If yes, what are the requirements to have this work?

Release notes mentioning being supported later on:

Documentation explaining the option, but not mentioning it not being supported yet.
https://docs.thinkwisesoftware.com/docs/sf/domains#add-dynamic-domain-input-constraints

At least on 2023.3 not seem to be able to make it work, but Indicium and the Universal GUI are up-to-date. Maybe 2024.1 is required, but I think the functionality is GUI located.