What the title says. It is for many people very immersion breaking when fields are build right in the center of the city on stone tiling.
See the whole thread here:
https://wildfiregames.com/forum/topic/38015-move-fields-away-from-the-cc/
So the idea here is to have fields that can be build anywhere (including neutral territory), but farmsteads who must be at least 90 meter away from the CC.
To compensate for that, the farmsteads provide a 30% farming rate increase around them and they are also buildable in neutral territory.
So strong city/ weak countryside if you will.
Why 90 meter you may ask? See here:
note that this still allows you to place defensive structures:
Also see note how this makes it easy to get berries outside of your territory for the price of being unprotected: