This is an example of what is usually called a flowchart proof (or sometimes a flow proof for short). A quick Google search for "flowchart proof" or "flow proof" shows many, many contemporary examples of the form, including a whole genre of YouTube videos teaching this style of presentation.
This style of proof has been promoted at various points since the ...
Judea Pearl & Dana Mackenzie, in their new book
The Book of Why
(p.190ff), explain the paradox in a way I hadn't seen before.
Pearl imagines changing the rules to "Let's Fake a Deal,"
where "Monty opens one of the two doors you didn't choose, but his choice is completely at random." Of course he could open the door
containing the car/prize, ruining ...