[wtallis]

It's actually probably reporting the software-configured resolution, not the hardware capability. The important distinction is whether it's a system-wide resolution setting or a game-specific setting that may not apply to browser contexts (except for the ones used by Steam itself).

[DeathRay2K]

What makes you think that it’s more likely reporting a software-configured resolution? It is after all a hardware survey, and focused on what user hardware supports.

[wtallis]

It's vastly simpler, and more useful, for Steam to detect the current resolution. Trying to detect the maximum supported resolution is non-trivial, especially when there are devices that will accept a 4k signal despite having fewer pixels.