This is referring to what you have your current window open to. As the website tells you, it’s “too brittle” because the value fluctuates quite a bit depending on what a person has their window set to. For example:
Maximized normal window:
Resized window:
Full Screen
In terms of WebGL Vendor & Renderer, this will show exact only if you have Graphics Acceleration enabled. This isn’t going to be randomized because it played a pivotal role in compatibility. As you can imagine, you are not the first person to ask about this and it’s certainly not the first time it’s been answered.
Below is a quoted excerpt from Shivan from Brave: