Surprised you didn't know this. This has been UL's requirement for decades for TV mounts.
To be clear however, that 4x rating is for it outright breaking (snapping). The mount will for sure be bending at less than 1/2 that. How and what the mount is anchored to will also determine how much it can take.

But the rating the mount advertises should be solid. Although I remember some people complaining about how much sag the SnapAV mounts had years ago. Not sure if they have improved upon that or not. Seems important however considering the tight tolerances you seem to have on this particular install.