Tom, the cheapest and easiest way to get an antenna away from Moteino is till just bare coax soldered to ANT and GND. The UFL is for modularity, but those connectors add to the cost quite a bit and hence they are not populated, but people can add one if they want to. For the rest of Moteinos the space is pretty tight, i have to worry about other things on there, and not sure how many people would take advantage of it. Even without the dedicated footprint coax is a good compromise and with a little care, a UFL can still be connected between the AND and GND pads on the bottom. Scraping some GND pour provides extra solder surface. It's not ideal I know but it's possible.
It's a tough call where to make the divide between the features of the different Moteino variants. It's like options on cars right?