I understand why he advocates a crowned board, but I wonder if it's "overthink"?
My planes have a lateral adjust lever, so do his, that compensates if the plane tips back. Plus, if the lateral lever isn't carefully adjusted then it will introduce an error way bigger than any cupped/crowned board error!
If I'm shooting with a cambered iron (and let's get real here, it's actually pretty tricky to sharpen without introduce some degree of cambering) then I adjust the lateral lever so that the apex of the camber when the plane is sitting on the shooting board coincides with the centre of the workpiece.
Each to his own, but this approach works for me. Dozens of times per year I use a long shooting board that runs along the bench to shoot the edges of narrow stock for drawer sides and drawer bottoms, this technique delivers shot edges that permit ultra reliable edge jointing.