Ahh, much clearer now:
It seems to be a custom joint, let me try to reverse engineer it :
1. So you start with indentations on the wood onto which you glue or otherwise affix your custom biscuits ( The metal or though plastic black bits you see in your picture )
2. I say is custom, because you have certain compression,tension and axial forces you already know, and you want it to be in that shape because you want to collapse the structure in 2 and make it easy to assemble, in any case the forces or sliding you want avoid are represented by the arrows.
3. The upper part (A) snaps with the bottom part (my sketch is a slightly different joint, but should give you an idea of what to look for ), and prevents sliding in the above mentioned directions, I believe you can still disassemble Miko Halonens one by rocking it back and forth and releasing the engaging teeth, but it's just a guess.
In the first picture you posted, I believe the mechanism is different, some push and slide metal fastener.
I used/ am fascinated by joinery of all types and it really is easy to figure out or come up with your own if you know about structural engineering a bit (look into Japanese joinery as well) ; run to the book store and get a copy of :
Structures: Or Why Things Don't Fall Down by j.e. Gordon