Just FYI, that info is now 10 years old. I recently researched switching to FreeBSD and found that the NVidia drivers don't support Vulkan, which is a requirement for DXVK to work, not to mention a lot of Linux ports. Can't comment on the other manufacturers' drivers though.
It's a 10 year old article. Of course the games are old. It might be that things are different now, or the same. But it still answers the question: Does steam work on FreeBSD (Yes), and is still accurate (Sometimes better)
Considering the age of the article, and the fact that I'm unable to find any information on Vulkan support for any manufacturer's drivers, I'm going to go out on a limb and say that Steam (more specifically Proton) doesn't work as well as it does on Linux.
It can be made to run, but I can't really recommend it unless you enjoy tinkering/troubleshooting. It's still pretty far from being a "plug-and-play" experience.