The IBM test is a great example of a ‘Wizard of OZ Experiment’. Apparently Facebook were doing the same thing for a while with their M ‘bot’ in Messenger (not sure if they still are).
In the field of human-computer interaction, a Wizard of Oz experiment is a research experiment in which subjects…en.wikipedia.org
I‘m not totally convinced by your newly termed coin for these kinds of early concept validation, but I think this is definitely something more people should spend effort on. I’m sure there’s plenty of bad ideas that went all the way to release that could probably have been scrapped much sooner.
You could also include things like designing the sales brochure/website before you design the product, or even writing a fake tech-blog article about it and testing people’s reactions to that.