A Thunderbolt cable has a Thunderbolt-connector on every end. A Thunderbolt-connector follows the Mini Displayport specifications and should be usable between Apple devices as such.
When I connect a Thunderbolt cable from my 2015 MacBook Pro (i7 4890k, AMD M370X, 16 GB, 512 GB) to my 4K-display (Acer S277HK), the display powers down immediately and I can't power it back up again until I've removed the Thunderbolt cable. Is this normal behaviour? Is the problem in the cable, the display or the display's mini displayport connector? Or are Thunderbolt cables generally not supposed to function as Mini Displayport to Mini Displayport cables?