Yeah, no worries 
I haven’t looked at Duimon’s preset, but the difference is probably because the default preset is using the integer scale settings in the shader parameters and Duimon’s isn’t. And he probably isn’t so that you can see more of the handheld body. To test you can go to the scaling settings and choose integer scaling mode 2 which is horizontal and vertical integer scale.
And now that I think about it I think tatsuya79’s handheld presents all use integer scale as well.
Edit:
Another thing to note is that one of the ds screens is 192px tall, the default preset screen is 384px tall (2x) and the screen in Duimon’s preset is 415px tall. Since it’s such a low multiple of the original resolution it’s not surprising its having a hard time distributing the pixels evenly with a strong grid pattern. A good question is if the standard lcd grid preset look the same at the same resolution. The way to test that would be to set a retroarch custom aspect ratio of the exact resolution and see what it looks like. Duimon’s screen that you captured is about 552x415

















