You guys might also be interested in the latest response from BenQ support:
‘Regarding why 1920 x1080 at 144Hz shows up while the monitor only supports up to 120Hz at this resolution, we have confirmed that this is a MacOS issue. When set to 1920 x 1080, the signal out put from Mac is still at 3840 x 2160, and the refresh rate is supported up to 144Hz at that resolution. In other words, due to the way MacOS works, the monitor is still detecting 3840 x 2160 from the source computer.
This is the same behavior on Mac's native screen if you change resolution settings, if you set at 3840x2160, everything on the screen looks smaller, but if set to a lower resolution, everything is then scaled up, but the actual resolution is still at the panel's native resolution.
And we have also observed that when selected the resolution from 2304x1296 to 3360x1890, the Mac's image is double pixel, so HDR cannot be selected, as there is not enough bandwidth left in this situation.
At the moment, as the issue is mainly caused by how Mac devices work with resolution, there is nothing we can do to improve the behavior. But you can rest assured that our team has requested Apple for some more information to follow up with the issue. We would encourage you to also contact Apple directly for further assistance on the issue.’