You have a point, but there are also lots of problems with this. How do we know it’s a real jhāna? Self-reporting is notoriously unreliable. The vast majority of people who think they have jhāna have nothing of the sort. And if you did find a proper jhāna meditator, how would you convince them to take part? They are likely to be utterly uninterested. I once foolishly suggested something of the kind to Ajahn Brahm, getting the dismissal I should have expected. But assuming you are a consummate salesman ( 
), would a confirmatory result really convince many people? Those who are already onboard would rejoice, whereas everyone else would say there is a flaw in the experiment or whatever. Just see what’s happening in parapsychology. As the Buddha says of psychic powers in DN 11:
Then someone with faith and confidence sees that mendicant performing those superhuman feats.
They tell someone else who lacks faith and confidence: ‘It’s incredible, it’s amazing! The ascetic has such psychic power and might! I saw him myself, performing all these superhuman feats!’
But the one lacking faith and confidence would say to them: ‘There’s a spell named Gandhārī. Using that a mendicant can perform such superhuman feats.’
I agree with you that it would be cool, but I can’t see it happen.