Isnt it a bit misleading to claim two Thunderbolt 2 "expansion ports"? One of them is an input from your computer isn't it? So there is no expansion of thunderbolt at all, just one port out for one port in (daisy chaining).
But the idea is like SCSI or Firewire. Every device should have 2 ports, one for input, one for output, meaning there will never be a lack of ports in any configuration. But of course, some devices like to ruin the fun by being an unwanted cul de sac.