What is this panel joint called? How to cut it?

[AndyT]

Thanks for the real world feedback.
The joint is in at least two books, but I suspect it might be theoretical rather than practical.
I wonder if any of the popular YouTube woodworkers have ever done a demo of it, instead of always showing dovetails? Or if anyone has ever spotted it in old work?

 

[Just4Fun]

Maybe it would mean little if nobody has spotted it in the wild because you could only recognise it after dismantling. So "never seen" might mean "never used" or it might mean "never failed". Either way, it is not for me.