The d3d12 documentation is less than complete. It uses the language "all UAV accesses (read or writes)" when talking about UAV barriers, but then only mentions "draw or dispatch calls" specifically. It's not really clear whether clears count. Has this test ever failed on Windows? Should we just add a barrier there anyway?
In dff22c9ed70811e4134c50d3d6d516b465e6a068 I ended up putting a barrier in what seems to be a similar case. My interpretation is that, absent better clarifications, it makes sense to consider clearing a write operation.