That is an interesting read. They are comparing "perceived black", which incorporates whatever effect ambient lighting is having on the panel as well. Quantum Dots react strongly with ambient light - I hadn't thought about that, but it makes sense. And it makes Samsing QD-OLED panels fare worse than VA and not much better than good IPS monitors.
It's hard to TLDR that article, they shotgun a lot of data out there.
This graph would be for most of your current generation LG screens (non-QD)
This one current generation QD-OLED - they use the same scale.
I will say, even though this graph clearly shows Glossy screens fairing better for perceived black - I hate trying to watch on glossy screens, because any amount of ambient lighting turns them into a mirror. It makes sense though, if you are measuring the effect of ambient light, a glossy screen is going to be the least impacted.
They do state at the end in their TL;DR (which is quite lengthy in and of itself and hard to parse without getting into the context up above) - that all the OLEDs were actually displaying true black - These graphs are just illustrating the effect of the ambient lighting and how it affects the screen and what we see sitting back on the couch. And this is just looking at that "black level" we see, it isn't looking at things like max brightness, color fidelity, HDR quality, features, etc. So just a very narrow, ver very detailed view at one aspect of monitor panels.