Agreed, it's not the distance on itself that is impressive, but the fact that it is achieved with very small off-the-shelf hardware, a short piece of wire as antenna, license-exempt ISM band, on a freely available IoT data network that you even can extend by placing a gateway yourself!
Indeed, this was pure line-of-sight, as the gateway was within the radio horizon of the balloon. Ground to ground would be more impressive, we have already seen ground distances with LoRaWAN of 320+ km due to atmospheric ducting. We'll look for more data and do a post about that later.
