I'm mildly confused as to the value over, say RustDesk. The latter allows remote control of external machines and has ip hole punching .. no hardware involved! Any takes here?

RustDesk is an alternative to other remote desktop software, JetKVM is an alternative to a built-in IPMI. It could be used as a remote desktop in a pinch, but that's not really the main point.

E.g. you'd use JetKVM-like devices to re-install your OS via emulated drives, remotely control power (including hard reset, not just WoL and software shutdown), change BIOS settings, or troubleshoot a crashing box - all without relying on any specific software/capabilities/behavior of the given box. Meanwhile you'd use remote desktop software when you just want the desktop to present itself remotely.

The advantage of KVMs like this is that it's a remove keyboard, video device, and mouse. That means that you can use it before the OS has started

Or without an OS installed at all, or with a broken OS.

I do VoIP phone systems for a living and this is why I deploy Supermicro mini-ITX servers, so even if something goes totally sideways as long as the client's IT is competent enough to get me remoted in to their voice network in some way I can troubleshoot it fully and in many cases fix it without leaving my desk possibly half way across the country. If it's an actual hardware problem and I can't fix it remotely I still then know for sure what's wrong and whoever's going on site can be properly equipped for the actual problem rather than having to bring everything.