The point is that if you run -x you will definitely see plenty of output leading up to the failure. It is true that if the command that fails outputs nothing to

The point is that if you run -x you will definitely see plenty of output leading up to the failure. It is true that if the command that fails outputs nothing to stderr, then this may still lead to confusing outcomes, but you will not be staring at empty output, you'll be staring at the commands leading up to the failure. This is of course no different than if you had set -e and then a command with no pipes failed silently without outputting anything to stderr. I don't personally see why this is notable in relation to pipefail.