My favorite is I have an HP Envy USB-C monitor to use with my Macbook, and using the HP factory supplied cable, every time I power it on I get a warning that I should use an "official HP USB-C cable". It's literally the one straight from the box!
I could be wrong though. I've got a similar setup and I've only seen the error once or twice.
I also refuses to mount my phone straight usb-c, and the known workaround is to go usbc -> a -> c.
At this point in my relationship with Apple, I can only assume this is deliberate.
I got the new xps13, it only has thunderbolt/USBc-C ports and it's pretty much 50/50 whether my external monitor will wake up.
I figured it was the cable and was about to buy another one but you saved me the trouble.
I also got a hootoo adapter that's supposed to support power delivery but that hasn't worked either :/