Right now, you can have planets with no surface water but with non-water-based xenobiology that end up with full-blown ecosystems full of trees. These can also be fully edible. The problem is that when you play these worlds, everywhere will be "too arid" for xeno farms even though the native flora is growing right there.
Assuming these edge cases aren't just oversights, I suppose the issue to be that there's supposed to be a resource management tradeoff with water for agriculture. If the plants don't need water, there's no input resource, and it's basically free food. However, the existence and spread of plants suggests that there's still some conception of arable terrain being worked out, so there would be room for making the output vary with the location - and the output could just be nerfed b/c of the difficulty of "watering" plants based on peroxide, sulfuric acid, etc. It may just be too much work for very rare situations, though.
More broadly, though... it would be nice if xeno areal didn't look the same as Terran areal. Ideally, xeno areal would match the local plant color palate for a given plantet, so e.g. if you were on a pinkish planet, you'd have pinkish fields instead of bright green ones...