I'm pretty sure that the reason that Flarm does not provide 3D information revolves around the fact that the data available is very limited. You can get some sense for your antenna performance only by collapsing a data set into a single plane to get enough points to do some averaging. Even though collapsed into a plane, the data is still quite granular. Remember also that each data point is not a measure of own ship performance; it is the composite performance of own ship and target ship Powerflarm systems. So averaging results from multiple ships is fundamentally necessary to get meaningful information. There just isn't enough data.