I suspect the difficulty of a Windows app is due to the fact that the Iro 2 is not an Internet appliance. I.e., it doesn't support having its own local LAN Internet address / doesn't have Internet server capability. The only way to 'talk' to it is via 'central command' in the cloud.
I have LAN connected HVAC (Ethernet) and natural gas water heater (WiFi) thermostats, all not unlike a sprinkler water 'thermostats' - turn something on/off based on a computer algorithm. A sprinkler controller you would think is not a lot different.
What's common to these examples is algorithm 'crunching' is done locally, within the LAN connected unit. OTOH, Iro2 is simply executing actions given to it by 'central command' (in the cloud). This makes sense because for 16 or 32 zones, it's a lot of number crunching to keep track of all of the ET variables.
In summary it makes sense to me that it's difficult to have a Windows app for the Iro 2. There's a lot of processing required for the Iro2 that's a lot easier to do in a cloud server versus locally.