You're right, good spot, I had actually made a personal proposal suggesting such an extension just a few weeks ago but I didn't think it was realistic enough for it to actually become reality. That's good news and, depending on routings, hopefully will improve service reliability (assuming the vehicle requirement will double - this will add room to pad the timetable and/or increase layover).
(
https://bustimes.org/services/lbao032 shows up to date traveline data on this. Like the Lothian Country routes the timetables, stops, routings themselves are not available yet).