I’m having this problem too, both with the copied example code (I have created the associated fields and supplied them with values) and also with a simplified block that should only show an <InnerBlocks /> component.
The block insertion area isn’t showing up in the editor and when I inspect where it should be, I see
<innerblocks></innerblocks>
Custom blocks created from scratch substitute a bunch of markup in there so it’s almost as if the '__experimental_jsx' => true
setting isn’t doing anything. Not sure what I’ve missed. Help?