Can you point to some source for that? I've never heard of a game using that resolution. The vast majority of them used the standard 320x200, either in CGA, EGA or VGA. The first two ran at 60Hz, VGA at 70Hz. A few games in the mid to late 90s started to use some non-standard tweaked VGA modes but by then Windows 95 started taking over gaming. You can check Wikipedia or Mobygames if you don't believe me.

Apparently the 720x400 mode is a text mode, according to: https://retrocomputing.stackexchange.com/questions/14806/why...

I would agree it's not a mode that was commonly used for vga dos games, which used lower resolutions around 300x200 and 8 bit color.