I think this might be Lottes, I’ll have to check.
So what auto does is double the mask size at 4k, it takes the pixel res of the shortest dimension of your viewport (E. G. Vertical res on a landscape orientation, or horizontal res on a portrait orientation) and checks if that is close to 2160. So I think it will not change on 1440p, which is probably good since your mask would appear visually larger than at 1080p.
I was looking for it in the folder: HSM-Mega-Bezel-Examples













