Since the monitor is external, I wonder if they've considered monitors as attack surface: https://github.com/RedBalloonShenanigans/MonitorDarkly
https://www.schneier.com/blog/archives/2014/03/ragemaster_ns...
There's no direct solution to the subverted monitor problem that I'm aware of. You basically get them from random places under different names or from people unlikely to be spies then use I/O protection both ways. Same with most hardware you can't produce yourself. There's potential to market something here where the monitor is immune to code injection, does I/O filtering, can't store anything, and does these with visually-inspectable chips & board. Add TEMPEST shielding while you're at it since that's an existing market that will drop lots of cash on improving security. See EMCON's products for examples.
EDIT: Forgot to mention that spectrum analysis is often used to try to catch radio emissions. There's techniques to tell if monitor sends out stranger than usual signals. That's just kind of limited and doesn't help if it's black bag job where person can show up twice (eg maintenance person).
The GP is 100% correct, if you can't trust your keyboard, mouse, and the monitor the "secure computer" concept in this case is problematic, while it does reduce the attack surface somewhat it just focuses the attention of the adversary onto a different vector.
If we take their "cleaning man/evil maid" scenario then while implanting the computer might not be possible, implanting the keyboard, mouse or screen would be very possible, and in fact somewhat easier than implanting a regular computer with decent security measures such as an encrypted drive.
Add a USB storage device with a micro-controller to the keyboard and you own the computer once it's connected, a monitor today comes with a CPU powerful enough to run custom code which can be used to exfiltrate data as well.
Additionally both the keyboard and the monitor could potentially be used to exploit software flaws on the software running on the ORWL unit also.
The concept is interesting however this is mostly "security theater" any adversary which would be sophisticated enough to require taking these measures would likely be able to circumvent them, and for the rest these measures don't really do anything; if you use this for day to day operations or on-net activity you'll get pwned via the network; if you keep secrets on this thing worthy of sending some one into your home to implant your PC then they'll implant something else which is connected to it.
Oddly enough the only "high tier" adversary that this might thwart would be law enforcement since their computer forensic SOP would pretty much melt down when encountering something which is tamper resistant.
But hey, you gotta start somewhere.
If you are going to prevent physical attacks from adversaries that can circumvent basic protection (e.g. FDE) you have to make sure that every device is as secure because the system is as secure as its weakest link.
If your adversaries are just the random person that might steal your PC then any full disk encryption even a cryptographically insecure one would be sufficient because the people who end up dealing with these devices won't have the knowhow or the resources to attack even bad encryption.