Staxrip: "Force crop values compatible with YUV/YV12 colorspace"?

[LaserBones]

I'm trying to trim 2 pixels off the top and bottom of an encode. In settings, there is an "Auto correct crop values" setting. When you hover over that setting it states "Force crop values compatible with YUV/YV12 colorspace and with the forced output mod value." I don't understand what this means or why a colorspace would have crop limitations. I know sometimes, for efficiency in encoding, you want a mod4 resolution. I've also read this isn't as important anymore. I'm not concerned about file sizes. Would turning this off allow me to crop any way I want? Do I need to keep things compatible for a YUV/YV12 colorspace? Any advice would be greatly appreciated. It's been hard to find info about this topic.

[_Al_]

Eexample, chroma plane could have smaller resolution that luma as YUV420 video (YV12). It has 1920x1080 for luma and 960x540 for U and V chroma. If you crop 3pixels fromtop, that would not work. Because you'd need to crop 3pixel lines for luma and 1.5 pixel lines for chroma. You need to crop only even number of lines for 420 subsampling (chroma has less resolution). Example cropping 4pixels, cropping 4pixels for luma and that crop would automatically crop 2 pixels for chroma as well. So in that case the mod is 2.