I can confirm this bug!
It happens to me as well. The instant I click "Tace Dump" checkbox Blender crashes.
Process: blender 
Version: 2.79b (2.79b 2018-03-22, Blender Foundation)
Date/Time: 2018-10-02 19:51:29.002 +0100
OS Version: Mac OS X 10.14 (18A391)
Report Version: 12
Bridge OS Version: 3.0 (14Y667)
Time Awake Since Boot: 55000 seconds
Time Since Wake: 42000 seconds
System Integrity Protection: enabled
Crashed Thread: 0 Dispatch queue: com.apple.main-thread
Exception Type: EXC_CRASH (SIGABRT)
Exception Codes: 0x0000000000000000, 0x0000000000000000
Exception Note: EXC_CORPSE_NOTIFY
This crash happens in all configurations.
Just MacBook Pro on it's own. And also when an eGPU is connected.
It is open Blender... set RPR as Renderer. Click About RPR and click Trace Dump = instant crash every time.
Thank's we're aware of the issue with multiple egpus and traces.
The displacement issue I think is related to subdivisons, investigating.