True, true, but currently they are used for building anyway, so I was offering an easy solution. Since it was gonna help building unless someone changes the way it works, it might as well do that. I guess @Imarok could remove the ability for worker elephants to build farms, but that's out of the scope of the patch. The goal of the patch is just to allow playing a different animation when a unit is building a structure, or a farm. That's it, that's the scope.
Making units go back and forth on the field sound nice however it's kinda complicated to do, as the person adding that feature would have to make it generic for every building , and every unit which has to take other units in account, shape of field, etc
No it means however that terrain textures would be used to define the fertility of the land. So while farmland terrain textures might serve purpose, any texture could. Like let's say grass_a or cliff_b
I think it's worth noting that while convoluted, the current one was way easier to implement And other than the lack of motivation to work on the paradigm, there were also very heated discussions about it, and it was not a trivial issue.