Yes, they are. Which is not related to the ports specifically, but the infrastructure behind it.
In short: on the Pi3 the USB port(s) and the ethernet chip ‘share’ access to the CPU, which means they share bandwidth as well. Which in turn means that there’s a limit to what can be achieved. This issue is not a problem when you’re doing 44.1k stuff, but as soon as you go higher (and use an USB DAC) you can run into issues.
On the Pi 4 this fundamental architectural issue has been resolved.
Thanks