On Tue, 12 Nov 2019, Clément Lassieur wrote:

> Does this[1] help?
>
> [1]: https://superuser.com/questions/730801/dd-immidiately-completes-but-actually-needs-sync

Indeed it does. I guess I just got lucky with the second invocation that 
data got written out. Thanks very much for the pointer, and sorry for the 
extra noise.

Since I no longer believe this to be a bug, I'm closing it.

Best,
Jack