I think you are mistaken. When I first start WGT with the Maxthon browser it opens with WGT default resolution. I then go into settings and select full screen which gives a much larger picture with no loss of quality so the limit is on the WGT end for full screen.
If my monitor was a standard 1920 x 1080 it would fill the screen so the limit is set by WGT for the screen resolution.
It is 2016 and most flat screen monitors have a much larger default size so in my view it is up to WGT to enable this,
I view all web sites in 2560 x 1440 ( 27 inch monitor ) and it fills the screen no problem with no black bars on the sides and no loss of quality. I even made our web site at that resolution but it will fill to overflow on a smaller monitor but that is no problem because all you have to do reduce the % and it will fill your screen to a value you prefer to look at the web site.
Just click on the 3 bars ( top right ) and reduce the percentage. Try it here www.scvcc.net