about a year or year and a half ago, the community decided against ultrawide. the ultrawide aspect ratio allows for two advantages in zvz:
1) increased "stickiness" or "homing/seeking power" of GA
2) increased reach for left-hand screen namelocks when using "screen space" video option
currently, there is some discussion about whether or not ultrawide aspect ratio should be allowed when playing in windowed mode (non-native resolution)
my opinion: ultrawide aspect ratios have been banned for more than a year, whether you're running d2 in your monitor's native res, windowed mode or stretched. 16:9 allows for a higher skill cap because a higher degree of precision is required for GA to seek opponent. all zvz ranked gameplay should be 16:9 aspect ratio (720p, 1080p, 1440p, 4k.)
we hadn't explicitly specified these rules before; we're getting around to it now. discussion below: