Review author here.
After digging through my motherboard manual, reading up on the AMD Ryzen 5 3550H APU I have, and digging through multiple Radeon and display settings, I was able to run the monitor at 1920x1080 @ 120 Hz and 1920x1080 @ 144 Hz.
As darkguy2 pointed out, the problem seems to be the APU. It cannot handle 4K at higher than 60 Hz. I've updated the review to reflect this.
I will say that, as I mentioned in the update in the article, 1920x1080 @ 144 Hz is buttery smooth with no screen tearing (thanks to AMD Freesync), so that's a plus.
Eve also let me know that the display itself is pretty much finalized; the company is primarily working on tweaks to the OSD, firmware, and adding in some ICs for additional features.
Long story short - if you're running a low-end GPU or any AMD APU, you're likely not going to get this to hit 4K/144 Hz, but that goes for any high-refresh-rate monitor.