Yes this is not a bug, the mod is designed atm to work with the game resolution set to 1080*2200 only.
when u're talking about playfield / game resolution, you're talking about the resolution set in Windows right?
Setting up your PC:
The resolution of the playfield must be set to 1080x1920.
Setting up the Game:
The game settings will require that the Back buffer width and Back buffer height maintain the same ratio as the default settings for the mod. Though the values recommended aren’t listed in the drop down menu, you can select each box and manually enter the proper values. All of these are valid and will work: 1080x2200 (default), 1620x3300 (1.5x default), 2160x4400 (2x default)
Setting up the Mod:
WindowStretch=293 This is the default value for proper aspect ratio. I Recommend not changing if you’re using a 1080x1920 display for playfield.