Thank you, @sob … I hope now people will stop spreading inaccurate information.
My short interpretation: the first diagram applies to WG mesh as well, the peers logic being hidden in the “switch” black box. Ethernet switch uses ARP table to select destination port, WG interface uses crypto-routing for the same. Ethernet switch learns MAC addresses automatically, WG interface is configured statically. Both magics only apply after packet enters the black box, usual L3 routing has to push packet into it (unlike black holes which suck data all by them selves 
)